Epidemiological Survey And Synthetical Prevention Of Haemosporidiosis In Endangered Cranes In China

Cranes(Gruidae)are considered as the 'flag species' for health assessment of wetland ecosystem,and some species are globally endangered with priority in conservation.In recent years,many death cases from haemosporidian infection in juvenile cranes were reported by Beijing Zoo and the other captive breeding sites in China.Our previous studies identified several haemosporidian parasites infected in cranes.In this study,we further performed investigation on epidemiology of haemosporidiosis in rare cranes in China.Distribution and epidemiological characteristics of haemosporidian parasites in different areas were identified through blood smear,pathological section microscopy observation and PCR detection,sequencing analysis and phylogenetic relationship analysis.Establishment of control measures by employing anti-mosquito greenhouse revealed excellents preventive effect.Our study laid the foundation for the scientific prevention and control of rare crane diseases in ChinaFirst,investigation of haemosporidian parasite infection from 104 crane individuals of 10 species in Beijing Zoo from 2007 to 2014 showed that the total infection rate was 23.08%(n=104).Haemosporidiosis is seasonal,and all cases occurred in the summer,reaching a peak incidence every 1-2 years.Juvenile cranes are more susceptible than adult cranes.There were mixed infections,usually with Plasmodium spp.and Leucocytozoon spp.Meanwhile,Plasmodium relictum is the dominant species of haemosporidian in Beijing Zoo.In addition,we conducted a survey of avian haemosporidian infection in 379 crane individuals from major breeding centers in 8 cities of 6 provinces,and the results showed that the infection rate was 37.99%(n=379).Infection of haemosporidian parasites occurred higher in summer,and infection rate in juvenile cranes was significantly higher than adult cranes.Infection rate in wetland conservations was higher than in city zoos.Eleven haemosporidian lineages including 5 Plasmodium spp,2 Haemoproteus spp and 4 Leucocytozoon spp.were identified,among which,5 species including P.relictum,P.homonucleophilum,P.elongatum,H.antigonis and L.majoris.Haemoproteus antigonis(GRUAME01)was the dominate lineage.Pathological observations revealed that the liver of the dead crane had a large number of black or brown red necrosis and white calcification.Hepatic,spleen,lung and kidney organs are severely hemorrhagic and necrotic,with a large number of schizonts of haemosporidian parasites.Next,a total 253 samples from 5118 blood-sucking insects of 4 species and 216 waterfowls of 31 species in the surrounding environment from Beijing Zoo,Zhalong,Xianghai and Delingha NatureReserve were collected for epidemiological investigation on infection source and vectors of haemosporidian parasites.Results showed that the detection rate in blood-sucking insects was 2.4%(6/253),and the detected lineages included P.relictum pSGS1,P.relictum P_XK13 and H.antigonish hOCHCAS01.The lineage of Haemoproteus spp.hOCHCAS01 detected from mosquitoes in Xianghai was the same lineage as the hGRUJAP01 and hGRUJAP02 detected from Grus japonensis in Xianghai and Zhalong Nature Reserve.The detection rate of haemosporidian parasites in waterfowls was 2.3%(5/216),with 4 dominant lineages:Plasmodium SW5,P.relictum pSGSl,H.antigonis GRUAME01 and Leucocytozoon sp.YY8.There are currently no effective treatment measures for haemosporidiosis in rare cranes in China.Cutting off the transmission route by establishing a mosquito-proof isolation breeding greenhouse for susceptible young cranes is an effective method to prevent this disease.Monitoring system of haemosporidian infection in large populations of captive cranes and high-density units is imperative and urgently need to be improved.On account of the variety of the prevalence and epidemiology in wetland nature reserve and in captive population of urban zoos,the prevention and control strategies should be formulated according to local situations.This study,for the first time,carries out an epidemiological survey of haemosporidian infection in 12 rare species of cranes.This study not only found new host of haemosporidian paraistes,established preventive control measures which obtained effectiveness,but also developed diagnostic procedures for the haemosporidiosis in cranes.Isolation of young cranes by greenhouses which turned out to be an effective method to prevent haemosporidian infection,is of great value for extensive application in city zoos.