Study On The Vector Of Camel Parabronemosis In China

Parabronemosis is a disease caused by the nematode-Parabronema skrjabini parasitized in abomasum of ruminant, among which camel is the optimum host. Inflammation, haemorrhage and ulcer in abomasum can be induced by the serious parasitism of P. skrjabini, which is also an important reason for the diarrhea and malnutrition in camels, and sometimes it could lead to the death of camels, which make it one of the most important diseases brought great damages to the camel industry and a great economic loss to herdsmen for a long time. But the life cycle and vectors of the nematodes were unknown and only a few articles had reported that some blood-sucking flies may be the vectors of P. skrjabini. But it is not clear that which kinds of flies can spread the disease in China. In addition, because the method of antemortem diagnosis is rare, it is difficult to carry out diagnosis and prevention of Parabronemosis in practice. So the research related to vectors of P. skrjabini was done in this study.Parabronemosis in 143 camels of different ages from 4 various camel breeding areas(Alashanzuoqi of Alashan, Siziwangqi of Wulanchabu, Wulatehouqi of Bayannaoer and Hangjinhouqi of Erdos)in Inner Mongolia were investigated. The results showed that the infection rate of Parabronemosis of camels was 81.8% in Inner Mongolia.The highest infection intensity was 1315 nemotodes per camel, and the proportion of female and male P. skrjabini was from 1.2:1 to 3.9:1.The infection and morbidity of old camels were both higher than the others and their pathological changes mainly showed ulcers, congestion, haemorrhage and mucosa shedding in abomasum of camels infected severely by P. skrjabini. Tissue sections showed that concentration and degeneration of epithelial cells of gland alveolu and infiltration of lymphocyte in abomasum tissue, and some vasculars full of erythrocyte were visible in the pylorus gland region.The possible vectors of P. skrjabini were studied through analysis of more than seven thousand flies captured in 3 main breeding regions of camels in Inner Mongolia(Alashanzuoqi of Alashan, Siziwangqi of Wulanchabu and Wulatehouqi of Bayannaoer). 25 species of flies belonged to 17 genera of 7 families and 2 other families (Coelopidae and Trixoscelidae) were not ascertained which genera belong to. Among them, 12 species were newly discovered in Inner Mongolia, including Musca asiatica, Musca cassara, Musca confiscate, Musca ventrosa, Haematobia irritans, Tachina flavosquama, Chaetopleurophora asiatica, Megaselia spiracularis, Lispe litorea, Morellia sinensis, Decia nigribasis and Norellia striolata. Besides, partial COI gene sequences of Haematobia irritans, H. titillans and Stomoxys calcitrans serving as the most possible vectors were studied in detail, and COI gene sequences of H. titillans were firstly determined. Then molecular taxonomy was used to verify morphological classification with rDNA ITS gene and COI gene.To select the Parabronemosis vectors, the flies of Coelopidae, Trixoscelidae and other 25 species were dissected and investigated under the stereomicroscope. Then, the nematode larvae suspected to be P. skrjabini were discovered from the horn flies of H. irritans and H. titillans, which distrubuted in the chest and mainly in the abdomen. The infection rate of male flies was 43.8%～48%, and it was 35.7%～46.2% in the female. The intensity was 1～22 larvae each fly. The larvae were spiral-shaped with different lengths. The 2 prominences around oral pore and the anus of the larva were easily observed under optical microscope. Digestive tract was obvious. The esophagus presarcoplasm and glandar part could be recognized. Besides, an unknown nematode was detected in Chaetopleurophora asiatica, which showed obvious differences from the larvae above.The specific primers of P. skrjabini (ST1 and ST2)were designed, the specificity of which was tested by the nematodes of 7 species which usually parasited in gastrintestinal tract of ruminant, including camels, and the horn flies with suspected Parabronema skrjabini larvae. The rDNA ITS gene of the larvae detected in the Haematobia irritans and H. titillans was amplified and sequenced. The result showed the homology of rDNA ITS sequences between the larvae (from H. irritans and H. titillans) and Parabronema skrjabini in GenBank were 99.2% and 99.3% respectively. It was identified that the larvae from horn flies were exactly the larvae of P. skrjabini, which indicated that H. irritans and H. titillans were the vector of Parabronemosis.The detection of P. skrjabini eggs put into feces were tested in laboratory by the methods of routine eggs examination (direct smear method, floating method and precipitation method ). The result showed that the eggs in the feces could not be detected by the routine methods. Then PCR and the Nested PCR methods were researched for examining eggs of P. skrjabini. The results indicated that PCR could be used to detect the eggs without any treatment, and the sensitivity of PCR and the Nested PCR methods were 15 eggs and 5 eggs in 25μL reaction system, respectively. So, P.skrjabini eggs could be directly used in the target partial sequence amplification by the PCR. It provided the basis for the molecular biology antemortem diagnosis of camel Parabronemosis.