Study On The Epidemiology Of Onchocerciasis And The RDNA-ITS Sequences Of Pathogen In Camels

Onchocerca of camels is a kind of white filaria nematodes. The adults mainly parasitize in the subcutaneous tissue, muscle tendons, ligaments and other parts of camels, and eventually cause the formation of fibrous nodules in the parasitizing sites. The camel onchocerciasis may brought great economic losses to the camel industry for its side effects on the quality of flesh and hide, camels’growth and development. At present, it is almost blank to study the pathogen of the disease, its vectors, the antemortem diagnosis and prevention. So it will supply importent basis for controlling the parasitosis to learn its epidemiology, species identification and phylogenesis. Based on the practice of camel industry in Inner Mongolia, the study was conducted to reseach the onchocerciasis from the following aspects.Firstly, the prevalence of onchocerciasis in camels was investigated in the Alashan area and the bayannaoer area, which were two main camels production region of Inner Mongolia. By parasitology dissection technology, in the experiment,64camels of different ages were dissected. The results showed that the infection rate of Onchocerca of camels was92percent averagely in Inner Mongolia. The highest infection intensity was23nodules of a camel, and the average size of the nodules was38×20×9(mm3).The intact adult female and male were gotten by digesting the nodules from the camels with pepsin, and the morphology of adults and microfilaria were described in detail. On the basis of identification by morphology, the16s rDNA gene in mitochondria were amplified by PCR, followed by cloning and sequencing to determine the species by molecular methode. The result showed that Onchocerca sp. from camels was Onchocerca fasciata exactly.Then, ITS1, ITS2and5.8S ribosomal DNA gene of Onchocerca fasciata were amplified with the nematodes universal primers NC5and NC2. The results indicated that the nucleotide sequence fragment length were412bp,341bp and157bp, respectively. Based on the ITS2sequence of Onchocerca fasciata and other species of Onchocerca, the homology was analyzed and phylogeny was constructed. The results showed that the homology was from93.2percent to97.3percent, and the data also revealed O.linealis was the most primitive species, and the evolution of O.fasciata, O.gibsoni, and O.gutturosa were later.The specific primers-OFIs and OFIas were designed, according to rDNA ITS sequences of O.fasciata, and the nematode genomic DNA was amplified. As indicated by agarose gel electrophoresis, the products were702bp. The specificity test also showed that the primers had a good specificity for O.fasciata, and they could be used to look for and ascertain the vectors of O.fasciata in camels by molecular methode.Anyway, it was the first time to describe the morphology of O.fasciata in bactrian camels and report the complete sequence of ITS and5.8S rDNA in China and abroad. So all these will provide important and basic materials for studies on the vectors of O.fasciata and its molecular biology in future.