Sero-epidemiology Of Hypodermosis And Molecular Taxonomy Of Hypoderma Spp Infective To Cattle And Yaks

Hypodermosis, caused by H. bovis, H. lineatum and H. sinense, is an important parasitic disease of domestic animals. It induces economic losses by reducing livestock products - the milk, the meat, the skin. There is fairly high infestation rate of Hypoderma spp according to statistics using the detection method of palpation warble on the back of infested animals during the spring and summer in northwest China in 1980s, and the average infestation rate arrives 80%. In some regions, 100% of cattle and yaks were infected. However, up to now, no any serodiagnosic methods for large-scale surveillance of hypodermosis have been developed, not mention to carry out the sero-surveillance in China. The researcher on the disease have different ideal about the taxonomy of H. sinense infective to the yaks on the plateau in China. Although there are some researching works on this subject based on the morphology and taxonomy by protein electrophoresist technology and found that there are diffemetia between the species of Hypoderma infective to cattle and yaks in China, some researchers considered H. sinense as a species besides H. bovis and H. lineatum, but others still insist that it's a subspecies of H. lineatum. To solve these problems on this field, a specific serological ELISA method for hypodermosis was developed by the antigen using the first larval of Hypoderma spp collected from infected animals in field for associating with control the disease by chemotherapy in the experiment. And then a large-scale serological surveillance was carried out using an enzyme-linked immunosorbent assay (ELISA) for investigating the situation of bovine hypodermosis in China. The molecular taxonomy of third instar larvae (L3) of Hypoderma, H. bovis, H. lineatum and H. sinense, infective to cattle and yaks which collected from different region in China, were studied using 18S rRNA and the cytochrome oxidase I (COI) gene sequence and constructed the phylogenetic tree and compared relatives of Hypoderma for acquiring the powerful evidence about its condition of taxonomy. The results show that the developed ELISA has high specification and sensitivity for hypodermosis, 96.15 and 97.09%, respectively, and can be used for sero-epidemiology surveillance of hypodermosis in China. The results of sero-surveillance show that there is still high infection rate on hypodermosis in China and the average infection rate is even up to 28.45%. The results of taxonomy indicate that H. sinense may be an absolute species of Hypoderma but not the high mountain subspecies of H. lineatum.