in 2006 , an unidentified respiratory disease occurred in rhesus monkeys 
 ( macaca mulatta ) at a breeding farm in the guangxi zhuang 
 autonomous region in southern china .
the farm , the largest in china , comprised 
 31,260 monkeys , of which 1 in 5 was unweaned .
the morbidity rate in young monkeys was 60% , 
 with an 30% death rate ( 25% and 5% , respectively , for adults ) . in 2007
, 
 surviving monkeys were vaccinated with an inactivated suspension made from the 
 livers and lungs of dead animals .
after vaccination , the number of cases decreased 
 during 2007 and 2008 to 100200 per year .
cases occurred throughout 2006 . because most authorized suppliers of monkeys to 
 research laboratories in china obtain their breeding stock from this farm , the 
 disease spread throughout china , particularly to experimental animal facilities in 
 wuhan , kunming , and beijing ( 14 ) .
the disease also was introduced into a few 
 wildlife parks in china ; however , perhaps because of the low population density of 
 susceptible animals in these locations , further spread has not been reported .
initially , cdv was not suspected as the causative agent of the monkeys 
 illness . in late 2008 , however , tissue specimens from infected animals that had been 
 stored in a freezer for 2 years were analyzed and found to contain cdv .
four serum 
 samples from adult monkeys whose illnesses had naturally resolved had titers of 
 432 virus neutralizing antibodies against cdv , whereas virus neutralizing 
 antibodies could not be detected in 3 serum samples from uninfected monkeys .
after 
 this identification , all experimental monkeys were vaccinated with attenuated cdv 
 vaccine starting in early 2009 . whether the vaccines actually boosted immunity or 
 whether they were simply given coincident with waning of the outbreak from 
 increasing immunity
, the number of cases has since remained low ( 130 in 2009 
 and 2030 in 2010 [ not all confirmed ] ) .
additionally , anti - cdv serum seemed 
 to help infected animals recover more rapidly from the infection .
infected monkeys initially displayed measles - like signs , including respiratory signs ; 
 anorexia ; fever ; and red rashes over the entire body , with reddening and swelling of 
 the footpads ; conjunctivitis ; and thick mucoid nasal discharge .
postmortem examination demonstrated discrete purple or rosy rashes on the body , with 
 macules of 24 mm ( figure 1 , panel a ) , 
 which in some cases were confluent and had a dark rosy color .
rashes on the face 
 were vesicular and ulcerated after suppuration , forming a scab .
other signs included 
 congestion , redness and swelling of the pars oralis pharyngis , diffuse hemorrhagic 
 spots on the papillae of the tongue , suppurative conjunctivitis ( figure 1 , panel b ) , and rhinitis with copious 
 thick mucous exudates .
blood stasis patches in the lungs and interstitial fibrosis 
 were observed in most affected lungs .
infected monkeys also had blood stasis in 
 parts of the liver , with tiny khaki - colored hemorrhagic spots on the surface .
a ) rash ; b ) 
 suppurative conjunctivitis . because of the signs of a measles - like infection , identification of the etiologic 
 agent first focused on measles virus and later on cdv .
reverse transcription pcr 
 amplification of lung specimens by using virus - specific primers was negative for 
 measles virus but positive for cdv .
the supernatant of ground liver samples also was 
 positive for cdv by immunochromatographic analysis ( bit rapid color cdv cassette , 
 bioindist co. ltd .
lung specimens also 
 infected tree shrews ( 12 months old ) after subcutaneous injection , resulting 
 in excitement and death from encephalitis and enterohemorrhage .
the full - length viral genome was amplified and sequenced ( genbank accession no . 

we constructed phylogenetic trees by the neighbor - joining method , using 
 the full sequence of this virus and others available in genbank .
the full genome of 
 this isolate shared the highest homology with a ferret isolate ( accession no . 

ay649446 ) from 
 the united states , and a dog isolate ( accession no .
the l gene showed the highest 
 identity ( 95.6%96.5% ) with that of us ferret and raccoon isolates ( accession 
 nos . ay386316 and ay466011 ) ; phylogenetic analysis of the h gene indicated an 
 eastern asian source of this isolate , which shared high homology with isolates from 
 different species of animals in china , taiwan , and japan ( figure 2 , panel b ) .
overall , the amino acid homology of the 
 guangxi isolate with the others was 96.0%97.3% , clustering it in a large 
 clade that includes cdv isolates from asia . nevertheless , the isolate is unique in 
 that it contains multiple amino acid changes in its viral structural proteins , none 
 of which have been found in other isolates .
phylogenetic analysis of the canine distemper virus by comparison of the 
 genome or gene of the monkey isolate with other canine distemper virus 
 isolates .
fx , fox ; cn , people s republic 
 of china ; rd , raccoon dog ; dg , dog ; tw , taiwan ; mky , monkey ; cnkm , kunming , 
 people s republic of china ; cnbj , beijing , people s republic 
 of china ; jp , japan ; dm , denmark ; pdn , lynx pardinus ; sp , 
 spain ; ft , ferret ; us , united states ; gm , germany ; bg , badger ; lp , lesser 
 panda ; mk , mink ; rc , raccoon ; lpd , leopard ; nl , the netherlands .
reasons for the epidemic remain unclear . the first monkey to contract the infection 
 was in the farm in guangxi ; however , the source of the infection is unknown because 
 there were no dogs or other fur - bearing animals at the farm .
breeding facilities 
 were self - contained , with no introduction of external animals and no other farms 
 nearby .
one possible 
 source of infection is contact by the monkeys at the farm with local wild monkeys
. 
 another possibility is spillover of the virus from a stray dog carrying cdv that 
 became adapted to the new host .
large - scale breeding and caging of the monkeys might have contributed to increasing 
 susceptibility to canine distemper infection . reared in groups of 2030 
 within fenced - off areas or in pens of several hundred ,
cdv appears to have been transmitted by droplets derived from feces 
 or other body discharges , all of which contained cdv .
this canine distemper outbreak poses a threat to monkey populations . because the 
 guangxi farm routinely supplies monkeys for animal facilities throughout china , 
 monitoring for canine distemper in its monkeys , including those shipped to other 
 animal facilities , as well as human handlers , is advisable to prevent possible 
 secondary spread and interspecies transmission .
although cdv spread has been largely controlled by inactivated and live canine 
 distemper vaccines , sporadic cases still occur and the high number of mutations in 
 the virus makes future transmission unpredictable .
therefore , surveillance for 
 canine distemper should be considered among monkey populations and among humans who 
 have close contact with them .
 since 2006 , canine distemper outbreaks have occurred in rhesus monkeys at a 
 breeding farm in guangxi , people s republic of china . 
 approximately 
 10,000 animals were infected ( 25%60% disease incidence ) ; 5%30% 
 of infected animals died . 
 the epidemic was controlled by vaccination . 
 amino acid 
 sequence analysis of the virus indicated a unique strain . 
The Study
Conclusions