Contents

Preface

Among the major devastating abiotic challenges is the salinization of soils, which are natural finite resources sustaining most life on Earth. Soils exhibiting saturation paste extracts (ECe) in the root zone as electrical conductivity (EC) > 4.0 dS m−1 (≈ 40 mM NaCl; dSm-1 = decisiemens per meter) at 25°C and 15% exchangeable Na+ ion are considered saline. By the year 2050, a projected increase of 16.2 million ha will be witnessed in salt‐affected areas. In terms of tolerance to salinity levels, plants are grouped into two categories, namely halophytes (salinity tolerant and adapted to salinized environments) and glycophytes (salinity-sensitive plants). Unfortunately, most agricultural crop plants are glycophytes (salt sensitive), where soil salinization adversely inhibits the plants' absorption of water and nutrients and eventually severely impairs the major physiological/biochemical and molecular attributes of crop plants as well as their yield (30%–50% reduction). Thus, the salinity sensitivity of most crop plants, increasing rate of land salinization, and salinity-caused losses in crop productivity are challenging food

Interestingly, the life of plants under salinity can be made easier and more productive by employing strategies comprising optimum and timely supply of mineral nutrients, compatible solutes, bio-stimulants, nanomaterials, phytohormones, phenolic compounds, and microorganisms, as well as considering the crosstalk of mineral nutrients/biostimulants–phytohormones and molecular-genetic approaches. These approaches, in isolation and/or combination, may boost the efficiency of the plant's inherent mechanisms for its improved sustenance and productivity under salinity

*Making Plant Life Easier and Productive Under Salinity – Updates and Prospects* introduces the concept of salinity, its major impacts, and important approaches for making plant life easier and more productive under salinity; reviews the scale and complexity of salinity impacts on Sri Lankan rice farming systems, along with presenting major actionable insights; reviews the salinity stress responses of major metabolites and in vitro production of terpene in plants; discusses the major mechanisms underlying phytohormone-mediated control of salinity impacts in plants; and appraises the literature on genomics-assisted breeding approaches for achieving salinity tolerance

We believe that this volume will serve as an important resource for plant biologists

We would like to thank our publisher IntechOpen for providing a platform for showcasing our work. We are also thankful to Publishing Process Manager Mrs. Karla

security.

stress.

in cereal crops.

and agriculturists as well as research students.


The ABO Blood Group System and *Plasmodium falciparum* (*Pf* ) Infection in Three Ethnic Groups Living in the Stable and Seasonal Malaria Transmission Areas of Burkina Faso (BF)

*Edith Christiane Bougouma, Alphonse Ouedraogo and Sodiomon Bienvenu Sirima*

## **Abstract**

Genetic factors, including red blood cell polymorphisms, influence the severity of disease due to infection with *Plasmodium falciparum (Pf)*. Studies show that these genetic factors associated with malaria susceptibility or resistance vary geographically, ethnically, and racially. We performed cross-sectional surveys in population living in rural villages from three ethnic groups. The blood group (BG) was determined genetically using two polymorphisms (rs8176719 and rs8176746). Out of 548 participants, 29.7% were Mossi, 38.2% were Fulani, and 32.1% were Rimaibe. The distribution of BG was, respectively, A: 25.5%, B: 26.6%, AB: 7.3%, and O: 40.5%. BG O was not only the common blood type overall, but was higher in Fulani (52.6%) than others. Fulani was associated with a reduced risk of infection and lower parasite densities than sympatric populations. The subjects with non-O blood were less susceptible to malaria infection. An association between ethnicity and malaria infection during the high transmission season as well as an association between the non-O blood group and malaria infections according to ethnicity was found. This was also true when ethnic groups were considered separately. Our results have demonstrated that the Fulani are not only less susceptible to *Pf* malaria infection, but when infected have lower parasite densities. Individuals with non-O blood are at lower risk of infection.

**Keywords:** ABO blood group system, malaria, *Plasmodium falciparum*, ethnic groups, Burkina Faso

#### **1. Introduction**

Malaria is one of the prevalent infectious diseases globally. In malaria-endemic areas, a significant proportion of children harbor parasites without presenting signs of clinical malaria and are considered asymptomatic cases [1]. Moreover, in communities where children are repeatedly infected with malaria, one can question why some children die while others do not. Variant-specific immunity may help explain chronic low-grade malaria infection without clinical symptoms [2]. A better knowledge of the polymorphic host genes associated with resistance to clinical malaria and/ or with high parasite densities might provide new insights into disease mechanisms, and suggest new approaches for prophylactic or therapeutic interventions [3, 4].

*Plasmodium falciparum* (*Pf*) has been called "the strongest known force for evolutionary selection in the recent history of the human genome [5, 6]. Indeed, the high mortality associated with *Pf* has given it the capacity to select emerging polymorphisms as rapidly as can be witnessed in evolutionary time [7, 8]. Several human genetic factors including red blood cell polymorphisms influence the severity of disease due to infection with *Pf*. To date, there is a paucity of information concerning the role of these host genetic factors (ABO blood group, sickle-cell trait, G6PD deficiency) in asymptomatic malaria, characterized by low-grade *Pf* infection and absence of fever/overt symptoms.

The ABO blood groups consist of A, B, and H carbohydrate antigens which can regulate protein activities during infection and antibodies against these antigens [9–11]. Several studies did try to establish an association between severe malaria and the ABO-blood group type [11–13], with some reporting significant associations on infection status and a particular ABO blood group [11, 13].

The relationship between ABO and malaria was first suggested more than 40 years ago [14]. Few studies have corroborated this hypothesis [8, 11, 14, 15], but some studies showed a weak association [2]. In India, for example, a significantly lower frequency of *Pf* infection was observed among individuals with blood groups A and O [9]. Thus, the selection pressures defining the ABO distributions remain uncertain with contrasting results between studies.

This study aimed to investigate the association between the ABO blood group and malaria susceptibility among Fulani compared to other sympatric ethnic groups living in Burkina Faso.

We offer four perspectives in support of this investigation:

#### **2. Brief review of malaria infection ABO blood groups**

For a long time ago, the ABO blood group system has been suggested to be associated with infectious diseases including malaria. ABO blood groups appear to protect against malaria, through loss of function due to a defective allele: the O phenotype of the ABO system seems to confer protection against *Pf* infection (see **Table 1**).

The human ABO gene consists of seven exons that are more than 18 kb in length and genomic analysis has found over 70 alleles at this locus, suggesting that it is one of the polymorphic genes in humans [1]. The three main antigenic classes (A, B, and O) are all comprised of numerous alleles in both coding and non-coding sequences [1].

The O alleles share a one-nucleotide deletion in codon 87 of exon 6 resulting in a frameshift mutation and premature termination of the polypeptide [2, 3]. O alleles are the most common of the three allelic classes (about 0.6 worldwide) and have frequencies between 0.3 and 0.7 in most populations. The A alleles generally have

frequencies between 0.2 and 0.3, and the B alleles have frequencies between 0.1 and 0.2 [4]. There is substantial evidence supporting the importance of allele O for protecting against malaria, based primarily on the consistency between the worldwide distributions of ABO variants and the historical presence of malaria. Uneke (2007) showed that the O allele, which is more frequent in malaria-endemic regions, is associated with greater resistance to malaria, in contrast to the A and B genotypes, which are less resistant [5]. Fry et al. [6] corroborated this finding through a study in three African populations showing a strong association of O individuals with resistance to severe malaria and a recessive effect in AO and BO individuals. Consequently, AO and BO would have the same susceptibility or sensitivity to malaria as AA and BB individuals; with AB genotype individuals being the most sensitive. The O allele is thought to protect against severe malaria through a mechanism of reduced reinitiation (*i.e.,* spontaneous binding of infected erythrocytes to uninfected erythrocytes) [7].

However, although the major O alleles share a one-nucleotide deletion, they differ in the number of nucleotide substitutions in both exons and introns. The O human alleles, although different from the O chimpanzee allele [8], are much older [1]. The most common O alleles, O01 and O02, are the result of separate mutations and are 1.15 and 2.5 million years old, respectively. In other words, assuming that the O allele protects from malaria, this protection may be a result of selection originally favoring O alleles for some other reason.

### **3. Method**

#### **3.1 Study area**

The study was conducted in four shrub-savanna villages located northeast (Barkoumbilen and Barkoundouba) and east (Bassy and Zanga) of Ouagadougou, the capital city of Burkina Faso (see **Figure 1**).

In the northeast zone, the Mossi and Rimaibè communities inhabit the village of Barkoumbilen, while the Fulani and Rimaibè inhabit the village of Barkoundouba. The Fulani and Rimaibe are present in both villages, so the Rimaibe represent an optimal internal control for the study. The two villages are 5 km apart. In the eastern zone, Mossi and Fulani communities independently inhabit two villages, Zanga and Bassy, about 1(one) km apart.

Malaria transmission in the study areas is hyperendemic and seasonal, with a rainy season from June to October. The entomological inoculation rate (EIR) is estimated to be around 200–300 infecting bites per person per year and is comparable between villages [6]. The main malaria vectors are *Anopheles gambiae* ss, *An. arabiensis* and *An. funestus*. *Plasmodium falciparum* (*Pf*) is responsible for more than 90% of malaria infections.

#### **3.2 Study participants and study period**

The population of the study area is predominantly of the Mossi ethnic group, followed by the widespread Fulani, who are generally closely associated with the Rimaibe (a hybrid of the two in terms of customs and even genetics). All three populations live in similar houses. However, the Fulani group, while adopting the habits of the sedentary Mossi populations, has retained their pastoral activities so that their habitat is characterized by the presence of cattle herds.

The total population of the four villages was obtained from a general census and enrolled in a demographic monitoring process. Except for children under 6 months

*The ABO Blood Group System and* Plasmodium falciparum *(*Pf*) Infection... DOI: http://dx.doi.org/10.5772/intechopen.102475*

#### **Figure 1.**

*Study site in Burkina. The study was carried out in four rural villages of shrubby savannah areas of Burkina Faso: northeast (Nioniokodogo and Barkoundouba), and east (Bassy and Zanga) of the capital town Ouagadougou. Compounds of the various ethnic groups are represented as capital letters. Inset/smaller map represents the study site relative to the whole country.*

of age, the entire population was eligible for the study and was characterized/ designated into two groups: participants aged 0.6 to 17 years and participants aged 18 years and older.

The study was conducted for two consecutive years and consisted of five crosssectional surveys (see **Table 2**).

i. Four surveys during the high malaria transmission seasons: in the middle of August 2007 and 2008; and in the middle of November/December 2007 and 2008.

ii.One survey in the middle of the low transmission/dry season: March 2008.

#### **3.3 Data collection**

Community sensitization meetings were held during which information or explanations about the context of the study, its objectives, its methodological approach, and the associated ethical issues were provided. The signing of written informed consent was a requirement for all study participants, including the guardians of minor children.

Following consent, a clinical team of physicians and nurses examined all participants for clinical signs of malaria, measured weight, and axillary body temperature. Suspected malaria cases (T ≥ 37.5°C) were treated with artemether and lumefantrine.

During the first cross-sectional survey, a two (2) ml venous blood sample was collected from all participants in EDTA tubes.

Thick and thin blood smears were prepared and the hemoglobin level was measured by the HemoCue technique.

#### **Table 2.**

*Population demographic.*

## **3.4 Laboratory methods**

### *3.4.1 Sample collection*

For each subject in this study, physical examination and capillary blood samples on slides and filter papers were collected. Slides were used for the diagnosis of malaria infection and the venous sampling was for the blood group characterization.

## *3.4.2 Blood slides*

Blood slides were stained with Giemsa for microscope identification of the *Plasmodium* species and determination of parasite density.

## *3.4.3 Malaria parasite diagnosis by microscopy*

Blood films were air-dried, the thin films fixed with methanol, and the slide stained with Giemsa. The slides were read by highly experienced laboratory technicians according to the site SOPs. Briefly, 100 high power fields were examined, and the number of malaria parasites/each species and stage was recorded. The number of parasites per microliter of blood was calculated assuming 200 white blood cells per high power field and a fixed white blood cell count of 8000/μL. A slide was considered negative if no parasites were found after the 100 HPF examination. Two independent microscopists read each slide and in case of discrepancy between the two readers, in terms of species, presence or absence of malaria parasites, or if the parasite densities differed by more than 30%, the slide was re-examined by a third laboratory technician. The arithmetic mean of the two closest readings was used as the final value of the parasite density. If there was no agreement after the third reading, the arithmetic mean of the three parasite densities was used.

## *3.4.4 DNA samples*

DNA extraction from the buffy coat (about 1.5 ml in volume) was performed using Nucleon BACC2 Kits. Successful DNA extraction was checked on a 1% agarose gel stained with ethidium bromide. A total of 2235 DNA samples (about 50 μl in

*The ABO Blood Group System and* Plasmodium falciparum *(*Pf*) Infection... DOI: http://dx.doi.org/10.5772/intechopen.102475*

volume) were collected: 825 from Mossi, 877 from Fulani, and 533 from Rimaibè individuals. Samples were stored in screw cap tubes labeled with the study code. Samples were kept at −20°C in cryo boxes. The DNA samples were shipped to the WTCHG in Oxford, UK, in May 2008. The DNA samples of study participants were genotyped at the WTCHG in Oxford, UK.

#### **3.5 Data management**

Demographic variables collected during the census of the four villages include for each person; age, gender, father and mother ethnicity, village, compound, family members and sequential number within the family, and census code. Assignment of ethnicity has been performed with the assistance of local guides.

The census data file was anonymized (name identification has been removed for privacy protection) according to the study protocol which was approved by the ethical committee of Burkina Faso. Clinical data were matched to the census data with study enrolment codes. Case report forms (CRF) for cross-sectional surveys were verified by the supervisor of the clinical study before data entry. Similarly, parasitological data were verified by the lab supervisor before data entry. Data entry was conducted by a team of computer engineers at Ouagadougou, Burkina Faso, and data files were validated by the database manager.

#### **3.6 Statistical analysis**

Data were entered into Microsoft Access. A Chi-square test was used to assess the difference between frequencies/associations between blood groups and *Pf* cases. ANOVA was used to test the difference between mean parasitemia.

Two-sided *p* values were reported, with differences considered significant at *p* ≤ 0.05. All analyses were carried out with the statistical software R 2.10.

#### **3.7 Clearance from National Ethics Committee**

The National Ethics Committee of the Ministry of Health (in Burkina Faso) granted ethical clearance. The study was conducted in compliance with the International Conference on Harmonization, Good Clinical Practices, the Declaration of Helsinki, and applicable Burkina Faso regulatory requirements. Individual written informed consent was obtained from each participant, participant's parents, or legally acceptable representative.

### **4. Results**

This study aimed to investigate *Pf* infection in Burkina Faso in the different ethnic groups: Fulani, Rimaibe, and Mossi according to the ABO group.

#### **4.1 Characteristics of the study participants**

A total of 548 subjects (380 children and 178 adults) were included in this study: Mossi, n = 163 (29.7%), Fulani, n = 209 (38.2%), and Rimaibe, n = 176 (32.1%). **Table 2** shows baseline demographic characteristics according to ethnicity. We did not find any significant difference among the three ethnic groups. The ABO blood group analysis in all children revealed that O antigen: 40.5% (222/548) was the most predominant, followed by A: 25.5% (140/548), B: 26.6% (146/548), and AB: 7.3% (40/548) antigens.

Blood group O was not only the commonest blood type overall, but was higher in the Fulani (n = 110 (52.6%)) than Mossi (n = 48 (29.4%)) and Rimaibe (n = 64 (36.4%)).

## **4.2 Malaria infection**

The malariometric indices for each cross-sectional survey are summarized in **Table 3**. The prevalence of *Pf* infection decreased from 51.6% during the high transmission season to 18.4% in the low season; the prevalence of clinical malaria also decreased significantly from 9.5% to 0.7%. The geometric mean parasite density according to the season (high transmission season and low transmission season) was represented in **Table 3**.

## **4.3 Malaria infection and ethnicity**

The study showed that during the period of high transmission, there was an association between ethnicity and malaria infection (*p* = 0.039). Subjects from the Fulani ethnic group were associated with a reduced risk of *Pf* infection (0.0001 and *p* = 0.02 for Fulani vs. Mossi/Rimaibe respectively during the start and end of the high transmission season). As a result, the Fulani ethnic group had lower parasite densities than the sympatric populations during the high transmission season: The mean density by ethnicity was 374 (251–557), respectively; 865 (598–1252); 483 (331–708) parasites/μl for Fulani, Mossi & Rimaibe (**Table 4**).

*The ABO Blood Group System and* Plasmodium falciparum *(*Pf*) Infection... DOI: http://dx.doi.org/10.5772/intechopen.102475*

#### *\*Survey number.*

*1: First survey, the middle of high malaria transmission season (August 2008).*

*2: Second survey, the end of high malaria transmission season (Nov 2008).*

*3: Third survey, the middle of the dry low transmission season (March 2008).*

*4: The fourth survey, the start of the high transmission season (July 2008).*

*5: Fifth survey, the end of the high transmission season (November/December 2008).*

#### **Table 3.**

*Malariometric indices according to the ethnicity group/survey.*

#### **Table 4.**

*Malariometric indices according to the ethnicity and blood group/season.*

## **4.4 Malaria infection and ABO blood groups**

The subjects with Non-O blood (i.e. A, B, or AB) were less susceptible to malaria infection (*p* = 0.011). We found also a significant difference when Non-O groups were considered separately (O versus A, *p* = 0.028; O versus B, *p* = 0.04; O versus AB, *p* = 0.0067). **Table 5** shows malaria infection according to the blood group. Parasitological data did not differ when comparing subjects with and without blood group O, the most prevalent blood group in the population sample.

## **4.5 Malaria infection, ABO blood groups, and ethnicity**

There was an association between the Non-O blood group of all ethnicities and malaria infections during high transmission. However, this association disappeared when the ethnic groups were considered separately (all ethnicities *p* = 0.011; Mossi: *p* = 0.56; Fulani: *p* = 0.59; Rimaibe: *p* = 0.49) (**Table 5**). Likewise, in the low transmission season, the difference in malaria infection between subjects with and without blood group O was not statistically significant (all ethnicities *p* = 0.86 Mossi: *p* = 0.72, Fulani: *p* = 0.94, Rimaibe: *p* = 0.91 On the other hand, a weak association between the Fulani and the Mossi with the

#### **Table 5.**

*The p values for the frequency of O and non-O blood group types between the three ethnic groups according to malaria infection and parasite density.*

antigen of blood group O and the prevalence of asymptomatic malaria was found (61.7% with the Mossi against 45.5% with the Fulani; *p* = 0.05). Considering the subjects of blood group B, the study showed an association between Fulani versus Mossi/Rimaibe, *p* = 0.001; Fulani versus Mossi, P *p* = 0.02 and Fulani versus Rimaibe, *p* = 0.003.

## **5. Discussion**

This study revealed that blood group O represented the most observed phenotype among participants (40.5%), followed by blood group B (26.6%), then blood group A (25.5%), and finally the AB blood group, which is rarer (7.3%). These results are consistent with those of previous studies that reported a high frequency of group O phenotypes in areas endemic to malaria [5, 9–13].

Other studies have corroborated this evidence by the inverse relationship: they have reported a high prevalence of blood group A and a low prevalence of phenotypes of blood group O in colder regions where malaria is an exotic disease [5, 10, 14].

These results would confirm the hypothesis of a selective evolutionary advantage (survival) of *Pf* infection on blood group O cells compared to other blood groups (A, B, or AB) in malaria-endemic areas [4].

The results of this study according to ethnicity also showed that Fulani were less infected with malaria despite their way of life and living in the same conditions of hyperendemic transmission. These were comparable to observations in previous studies in Burkina Faso and West Africa [15, 16].

Like the study carried out in Gabon by Monbo et al. [17], this study showed a high prevalence of malaria infection in participants with blood group O compared to participants with blood groups A, B, or AB; and is in contrast to previous studies that suggested individuals of blood groups A, B, and AB is more susceptible to *Pf* infection than group O [6, 18].

Lower parasite densities in subjects of blood group O compared to non-O subjects were observed, but the differences were not statistically significant. These observations are in line with the conclusions of previous studies which have shown that patients with blood group O were associated with increased protection against parasitemia [18–23].

These results would suggest a protective effect of the O antigen against clinical malaria. However, other explanations, such as the anti-rosette formation effect associated with blood group antigens, should also be considered [24].

In any case, this study made it possible to establish the involvement of Fulani groups against malaria infection and parasitemia. It also revealed that for all ethnicities combined, there would be a statistically significant difference in susceptibility to malaria between participants of blood groups O and participants of other blood groups (A, B, and AB).

The absence of any statistically significant difference in susceptibility to malaria in an intra-ethnic blood group analysis could be due to a sample size effect. Hence, the need for in-depth and broader epigenetic studies to accurately capture the effects of ABO blood groups in susceptibility to Pf malaria is highlighted.

### **6. Conclusion**

The study confirmed that the Fulani group is less susceptible to *Pf* clinical malaria and when infected had generally lower parasite densities. The study also *The ABO Blood Group System and* Plasmodium falciparum *(*Pf*) Infection... DOI: http://dx.doi.org/10.5772/intechopen.102475*

found that despite infectivity being more frequent in blood group O, individuals of this blood group are at less risk of clinical malaria and have low parasitaemias compared to individuals of other blood groups (A, B, or AB).

Evidence of correlations between ethnicity and blood group at risk of malaria infection would support the idea that the presumed association between blood group and malaria infection depends on the demographic distribution and characteristics of the population studied. As a result, each region of the world has a characteristic ABO phenotypic distribution, making it urgent to fully understand the biology of malaria infection through detailed studies of the interactions between the ABO blood grouping system: A critical condition for saving lives in malaria-endemic regions.

## **Authorship contributions**

BEC wrote the manuscript and agree to be accountable for all aspects of the work.

AO and SBS read and approved the final manuscript and agree to be accountable for all aspects of the work.

## **Conflicts of interest**

The authors have declared no conflict of interest.

## **Ethics approval**

The study received approval from the ethical committees of the Ministry of Health of Burkina Faso.

## **Acronyms and abbreviations**

*Blood Groups - More than Inheritance of Antigenic Substances*

## **Author details**

Edith Christiane Bougouma\*, Alphonse Ouedraogo and Sodiomon Bienvenu Sirima Groupe de Recherche Action en Santé (GRAS), Ouagadougou, Burkina Faso

\*Address all correspondence to<EMAIL_ADDRESS>
© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*The ABO Blood Group System and* Plasmodium falciparum *(*Pf*) Infection... DOI: http://dx.doi.org/10.5772/intechopen.102475*

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## **Chapter 9**


*5.1. Land Tenure Disputes*

As noted in the results part of this study, high frequencies of respondents in peri-urban areas are victims of land tenure disputes compared to those from rural areas. This finding has also been documented in other studies. For instance, Mbiba and Huchzermeyer [62] noted that peri-urban areas in Africa are dominated by land-related disputes. Though there are locational variations, land can be seen as the direct or indirect source of most disputes in agrarian societies [52,63,64]. In most developing countries, even if horizontal urban expansion is the major cause of peri-urban land disputes [38], the problem is exacerbated in situations where there is a lack of sound spatial planning and where there are institutional problems, inadequate compensation payments, and the absence of effective land tenure security for all landholders [6,49,65]. In addition, in a study conducted in China, it was reported that the lack of institutional competence, i.e., the exercise of power by lower governments without getting into agreements with farmers and inadequate compensation payments, are the main causes of land expropriation disputes [66]. Different types of land disputes were identified in the study. These are boundary disputes, landholding disputes, land rental disputes, divorce-related land tenure disputes, land bequeath disputes, parcel exchange disputes. and land use-related disputes. Boundary disputes are disputes which arise due to trespassing of the parcel boundary between bordering parcel owners/holders and can arise between individuals, between groups, between public agencies, and between individuals and public institutions [10]. From the identified plethora of land disputes, boundary trespassing disputes are the most dominant. The lack of surveying to fix cadastral boundaries is the main challenge even if land has already been registered. Researchers in other African countries also confirm that boundary disputes constitute a significantly high share of land dispute types [12,46,47]. As confirmed in this study, the asymmetric boundary conflicts between municipalities and individuals are a complex challenge for peri-urban landholders. The boundary between urban and peri-urban territory is obscure. Urban municipalities usually want to have control over the surrounding land, assuming that it is municipal land, while suburban landholders claim rights to challenge the supremacy intentions of municipalities. As confirmed by the participants of the focus group discussions, this has increased the incidence of landholding disputes in peri-urban areas and leads to greater tenure insecurity for peri-urban subsistence farmers.

Since 2007, the territory of Debre Markos town has expanded by about 5 km in all directions, based on the municipal master plan. As a result, former rural areas have been designated as urban areas and landholders whose houses are within the expansion radius are assigned as residents of the urban areas. These are the areas which face institutional problems of land administration. For example, as reported by a farmer in the interview, some of his parcels are now dedicated to urban territory, while other parcels are still registered as rural areas. One parcel even is bisected into urban and rural territory. As the rural land administration institution is responsible for the portion of the parcel in the rural territory and the urban land administration institution is responsible for the portion designated to the urban territory, the landholder sometimes faces contradictory rules. For instance, the rural land administration legislation allows the landholder to use the land for houses, agriculture, animal husbandry, forest management, or other activities, if no written land use plan has been prepared by a competent body (often land use plans are

absent in peri-urban areas). In contradiction, the urban land administration rule prohibits constructing or renovating buildings or fences without building permits. Constructions of any sort may lead to sanctions and even demolition. Thus, peri-urban landholders are sometimes subject to two different sets of regulations from two different authorities, which jeopardize the security of their land tenure and leads to disputes. Deininger et al. [40] and Nega et al. [67] have also noted that the unclear assignment of institutional responsibilities causes land tenure conflicts. Peri-urban expansion by a municipality is often not based on a sound spatial plan but on the spontaneous desires of a municipality [49]. Property rights in peri-urban areas are often uncertain due to a lack of institutional arrangements to manage peri-urban land [67]. To manage these areas by urban administration is challenging since the focus of the municipalities is to expand urban territory by expropriating peri-urban land. Most of these land disputes are interest-based disputes since they are competing for the scarce resource of land.

As noted in the result part of the study, the three predominant types of peri-urban land use disputes are inappropriate waste disposal, misuse of land, and communal land encroachment. The municipality of Debre Markos town disposes waste materials in the surrounding peri-urban areas haphazardly without taking into account the consequences of their actions for the well-being of peri-urban dwellers. Both liquid and solid waste materials are disposed of at open-air waste sites, which are expanding over time by consuming productive agricultural land. Even the land near the disposed waste material cannot be properly cultivated because of the noxious smell of the waste. Some wastes, like plastic cases, are also blown by wind and pollute other properties. Face-to-face interviews carried out in the study gave evidence that peri-urban landholders are concerned by this abhorrent a situation, as they are affected in multiple ways. They are victims of expropriation, and their landholdings are being polluted and spoiled by waste. Consequently, landholders are suffering from the unpleasant smells due to environmental pollution. These findings are in line with those of other studies. Allen et al. [51] also noted that peri-urban areas are often used as waste disposal sites, while Alemu et al. [68] noted that many peri-urban dwellers spend their whole lives in polluted environments. The municipality, responsible for waste disposal, has never consulted the peri-urban farmers about the suitability of sites for waste disposal. Even though the active involvement of the affected farmers and discussion with the relevant stakeholders are essential to reduce land disputes, the lack of participatory land use planning is one of the basic challenges of peri-urban land management in most African countries [69,70].

The current economic growth in Ethiopia is exhibiting promising results. The government desires to transform the country from an agrarian economy to industrialization based on agricultural development. Thus, the policies promote small enterprises as well as medium- and large-scale industries. Most of the private and public enterprises find it the most feasible to establish their firms close to towns. Thus, peri-urban areas become primary choices for investment by many governmental and non-governmental organizations, and the municipalities incorporate industrial zones in their master plans in the peri-urban areas. Accordingly, Debre Markos has delineated industrial zones along the urban fringe in its master plan. For the establishment of this industrial zone, the authorities expropriated many parcels and transferred individual land to municipal ownership. After the transfer, the municipality usually makes this land available to those coming with development projects and with the intention to establish firms. However, some of those firms are abusing land. For instance, enterprises carry out earthworks to construct company buildings and infrastructure and indiscriminately dump the excavated material, polluting peri-urban grazing land. It would be better to transport the excavated soils to the hinterland and use them for filling eroded gullies and ravines, even though this would be more expensive.

In Amhara National Regional State of Ethiopia, there are four types of landholdings: private, common, communal, and state property [71]. Private, communal, and state property regimes are similar in definition to those terms in different literature [72,73], though landholders lack exclusive rights in the case of Ethiopia. The use of the term common

property regime differs in Ethiopia from other countries: this refers to a property type commonly held by small groups of individuals. In order to minimize land fragmentation, the minimum parcel size (0.25 hectares) is specified in the rural land administration Regulation No. 159/2018 of Amhara National Regional State [74]. Thus, if any property formation measure results in an area of less than 0.25 hectares, two or more individuals will own the parcel commonly as common property [23,71,74]. As noted in the results of this study, disputes on this type of property regime are few in number. The main reason for this is that the common landholding regime is found in small amounts in peri-urban areas and the nearby rural kebeles. Disputes on this property regime are expected to increase in the future, however, because land fragmentation is legally prohibited and there will be many common landholders.

As with common property regimes, disputes on state property regimes are also few in number. However, in some areas, state property regimes in lowland areas are becoming sources of dispute between the local community and investors engaged in agricultural production [16,75–77]. This is because some farmers have possessed land in these lowland areas informally, and because of increasing immigration to these formerly remote areas.

Although the rural land administration proclamations grant full rights to communal landholders [23,71], these rights are not properly practiced. The absence of clearly defined property rights to communal land [23] and a lack of enforcement contribute to increased competition and encroachment on the communal land. The registration for these property regimes is not well managed and even the book of possession has not yet been issued, and as a consequence, compensation is not often paid for the expropriated communal lands. When farmers raise the issue to the municipality, they are told that it is the right of the municipality to use communal land for urban expansion without paying compensation. Communal property regimes in peri-urban areas are targets of expropriation by municipalities. This finding is confirmed by Puppim de Oliveira [78], who also observed that municipalities focus on expropriating communal property regimes without titles.

The encroachment of communal land generally increases problems in peri-urban areas. This is because farmers, who have parcels adjacent to the boundary of the communal land, assume that converting pastures into arable land is a way to get at least some compensation in the case of expropriation. For this reason, farmers whose plots border communal land are encroaching on it and converting communal grazing land into arable land. During the past few decades, communal forests have been encroached upon to such an extent that there are only sparse areas left. Currently, communal grazing lands are becoming new areas of interest for encroachment, even though this has a detrimental effect on the livestock sector.


**2. Cubic Silicon Carbide (3C-SiC): Structure and Material Properties for Power Electronic Application**

The cubic form of SiC, coined '3C-SiC', is one of many stable polytypes characterised by its wide bandgap and bilayer stacking sequence of ABCABC . . . [7]. The resulting structure is a pure zinc-blende exhibiting an energy band gap of 2.3–2.4 eV [8], lower compared to other major SiC polytypes, but with a higher electron mobility and saturation velocity owing to its higher degree of symmetry. Although 3C-SiC has a smaller energy bandgap compared to its wide bandgap counterparts such as 4H-SiC and GaN, this material displays isotropy for many of the desired power device material characteristics such as avalanche coefficients and high electron mobility [9,10]. Another advantage of 3C-SiC is its relatively large thermodynamic stability meaning that bulk material can be grown at reduced thermal budgets (below 1500 ◦C). Table 1 shows the important physical and electrical properties of 3C-SiC compared to other commercial power device materials such

as Si, GaN and 4H-SiC. Likewise included are promising oxide and nitride ultra-WBG materials. The 3C-SiC intrinsic carrier concentration (~10−1 cm−3 ) is several orders of magnitude lower than in Si, but not as low as 4H-SiC or GaN. Moreover, 3C-SiC has a thermal conductivity three times that of Si. Consequently, 3C-SiC devices should have lower leakage currents with the ability to operate at moderately higher temperatures when compared to Si and GaN. Other key aspects are the reasonable critical electric field value resulting in a higher breakdown of the material. On analysis of these material properties, 3C-SiC is a promising semiconductor for power semiconductor devices in the region of 600–1000 V. On reflection, there exists the possibility to obtain a targeted breakdown voltage (VB) with thinner, more highly doped drift layers, which results in a significant reduction of the specific on-resistance (RON) compared to Si devices. Therefore, devices that are smaller and more efficient can be fabricated, minimizing both the static and dynamic losses.

**Table 1.** Appropriate physical and electrical properties of cubic silicon carbide (3C-SiC) compared to other wide bandgap materials (data taken at 300 K).

Note: a is mobility along a-axis, c is mobility along c-axis, \* refers to an estimated value and \*\* refers to the 2DEG mobility.

> The 3C-SiC Baliga figure of merit (BFOM) and BFOM for high-frequency, high-power unipolar switches (BHFFOM) [11] are 140 and 25, respectively. These values seem very modest compared to the equivalent values for more advanced WBG power semiconductors such as 4H-SiC and GaN. These key performance indicators for power semiconductors quantify the minimum conduction loss during DC operation (BFOM) and the minimum conduction loss at high frequencies (BHFFOM). Indeed, examination of these values suggests that lower resistance devices are possible based on 4H-SiC and GaN when compared to 3C-SiC. However, this advantage must be weighed against power device reliability and field lifetime within a converter application. In this regard, 3C-SiC is the clear winner, benefitting from a favourable metal-oxide-semiconductor (MOS) interface when compared to its 4H-SiC counterpart. The bandgap value (Eg) for 3C-SiC was reported by Bimberg et al. [12] and later by Goldberg et al. [8] (see Table 1). Figure 1 shows the conduction band offsets of the major power semiconductors with silicon dioxide (SiO2). From the figure it is seen that the band offset (ΦB) between 3C-SiC and SiO2 is 3.7 eV. This is significantly larger when compared to the other power semiconductors with their values ranging between 2.7 eV–3.2 eV.

> The ramifications of this important property are realised in terms of reduced gate leakage current for a given oxide electric field. The important current transport mecha

nism which relates to this physical parameter is the Fowler-Nordheim (F-N) tunnelling mechanism. The F-N tunnelling current is given by:

$$J\_{FN} = \frac{A}{\Phi\_B} E\_{\text{ox}}{}^2 \exp\left(-\frac{B\Phi\_B^{3/2}}{E\_{\text{ox}}}\right) \tag{1}$$

where *Eox* is the oxide electric field, Φ*B* is the barrier height and A, B are constant values. It can be seen that due to F-N tunnelling the oxide electric field value must be reduced by 2–3 times in 4H-SiC compared to the 3C-SiC system.

**Figure 1.** Major power semiconductors' band structure for 3C-SiC, 4H-SiC, 6H-SiC and silicon, illustrating band offsets with silicon dioxide (SiO2 ).

Fardi and Van Zeghbroeck [13] developed an empirical breakdown field model based on the breakdown voltage and field values that were obtained from published experimental data [14,15]. This proved to be more than adequate for 3C-SiC device design, having matched electrical breakdown characteristics to many published reports. Moreover, the model has been utilised in commercial 2-dimensional device design suites [16–18]. Fitting these impact ionisation coefficients to the electric field and substituting into the impact ionisation integral leads to closed-form solutions of the breakdown voltage and depletion layer width. These material parameters allow for the initial stages of power device design. The closed-form solutions for the breakdown voltage and parallel-plane depletion region width are given as:

$$BV\_{PP} = 7.88 \times 10^{14} N\_D^{-3/4} \tag{2}$$

$$\mathcal{W}\_{\rm PP} = 9.12 \times 10^{10} \text{N}\_{\rm D}^{-7/8} \tag{3}$$

where *BVPP* is the breakdown voltage, *ND* is the doping concentration and *WPP* is the parallel-plane depletion region width. The breakdown voltage and depletion region widths predicted by Equations (2) and (3), respectively, are shown in Figure 2.

**Figure 2.** (**a**) Parallel plane breakdown voltage (*BVPP*) and (**b**) depletion width (*WPP*) as a function of doping (*ND*) for 3C-SiC.

#### **3. Processing Technology for 3C-SiC**


**Application of Thermo-Viscoelastic Laminated Plate Theory to Predict Warpage of Printed Circuit Boards**

Takaya Kobayashi, Masami Sato and Yasuko Mihara

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/49978


**13. Conclusion**

Birth defects or congenital anomalies are important cause of perinatal mortality and morbidity. In developed countries successes were achieved in screening, treatment and prevention over the years. In Africa the picture is different as many factors play a role in causing congenital anomalies different from those seen in developed countries. In Africa factors such as poverty, illiteracy, malnutrition, exposure to teratogens and poor environmental control play an important role. Screening, treatment and preventive services for congenital anomalies are poorly developed. To achieve control primary prevention should be established and strengthened and when this is achieved, then secondary and tertiary control should follow. Innovative strategies should be employed in this endeavor.

**Author details**

Kano, Nigeria

**211**

Labaran Dayyabu Aliyu

Obstetrics and Gynecology Department, College of Medicine Bayero University,

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