| Yak is a special species in Qinghai Tibet Plateau, which is a major economic animal for residents and herdsmen living there. The parasitic disease in Yak have been an important disease seriously harmful to the Yak breeding industry. In this decades, only a few researches on Yak's internal parasitic diseases in Hongyuan county and Litang county were reported, which resulted in the deficiency of the relative epidemiological data in that area, and brought a great difficulty to the prevention and control of these diseases in yak.In this study, using the modified Liao's counting method, the parasite eggs or oocysts were observed and counted in total 402 fecal samples of Yaks collected from Hongyuan county in Aba prefecture and Litang county in Ganzi prefecture. The investigation on infection of Yaks' internal parasites was conducted to obtain the latest epidemiological data of these diseases.This study obtained the following results:1. Observation of the parasitic eggs or oocysts in fecal samples showed that, the main parasite infecting Yaks in partial area in Hongyuan county and Litang county were nematodes, cestodes, trematodes and coccidian. The average infective dose(eggs per gram, EPG) of nematode eggs in Yaks in deferent farms of Hongyuan county was 34.52 to 4.26, that of cestodes eggs was 39.29 to 9.57, that of trematodes eggs was 68.63 to 11.90, and the average infective dose(oocysts per gram, OPG) of coccidian oocysts was 33.33 to 3.26. The average infective doses(EPG or OPG) of nematodes eggs, cestodes eggs, trematodes eggs and coccidian oocysts in Yaks of Litang county were 52.38, 13.1, 20.24 and 1.19 respectively. Totally the average infective doses(EPG or OPG) of these four kinds of parasitic eggs or oocysts in Yaks in these two counties were 15.67, 22.64, 40.8 and 13.43 respectively, in which the infective strength of trematodes eggs was the highest. The average infective dose of total 4 kinds of parasitic eggs or oocysts in Yaks in these two counties was 92.54 EPG, in which, that of the Yaks in Hongyuan and Litang county were 154.90 to 48.91 and 86.90 respectively.2. The average infective rates of main internal parasites, including nematodes, cestodes, trematodes and coccidian, were 21.14%, 34.58%, 42.79% and 15.92% respectively in Yaks in partial area of Hongyuan county and Litang county. In which, the average infective rates of these 4 kinds of internal parasites of Yaks in Hongyuan county were 17.5%(47.62% to 6.38%), 36.39%(57.14% to 17.02%), 45%(60.87% to 19.05%) and 17.5%(29.41% to 6.52%) respectively, and that of Yaks in Litang county were 52.38%, 19.05%, 23.81% and 2.38% respectively. The total infective rate of main internal parasites in Yaks of two counties was 76.337%, in which that of Hongyuan and Litang county were 76.11%(86.27% to 58.7%) and 78.57% respectively. This result showed that the infective rate of internal parasites of Yaks in partial area in Hongyuan county and Litang county is high and the harm is great.3. The infective rates of single infection, double infection, triple infection and quadruple infection of 4 kinds of internal parasites of Yaks in partial area in Hongyuan county and Litang county were 45.27%, 24.63%, 5.72% and 0.75% respectively, in which the results in Hongyuan county were 44.17%(47.83% to 39.13%), 24.7% 36.11% to 12.77%), 6.39%(11.9% to 0%) and 0.83%(2.17% to 0%) respectively, and the results in Litang county were 54.76%, 23.81%, 0% and 0% respectively. These results indicated that, the infection of main internal parasites in Yaks in partial area in Hongyuan county and Litang county mainly were single infection and double infection, which accounted for 69.90% of the total infection rate.The results in this paper enriched the epidemiological data of Yak's parasitic diseases in Hongyuan county and Litang county, which can provide a theoretical basis for the prevention and control of parasitic diseases in yak. |
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