Observations of Parabronema skrjabini in Horn Flies and Analysis of Its Specific Sequences within COI gene Abstract Parabronema skrjabini is a nematode parasite in camels’abmasum and its vectors are Haematobia irritans and Haematobia titillans. In order to ensure the infection, classification and establish an antemortem diagnosis method, the paper do the research about three parts: survey the infection rate, analyse sequences of COI gene within mtDNA, design specific primers. The results as follows: 176 horn flies (64 and 112 ) from Wulatehouqi of Bayannaoer city in Inner Mongolia of China were dissected, then the infection rate and infection density were calculated. The results show: 38 horn flies were infected and the infection rate was %. Therein, 13 were infected which infection rate was %, the highest infection density was 32; 25 were infected which infection rate was %, the highest infection density was 23. was parasited in the digestive tract. The COI gene of from three different aeras of Inner Mongolia in China was amplified by PCR using universal primers. Then the PCR products were sequenced and analysed. The result showed that the COI gene was 689bp and there were no differences among three samples from different aeras. Comparison with sequences of COI gene from the family in Spirurata and Filariata reported in GenBank, the percent identity was between % and %; the nucleotide pairwise distance was between and . ic tree based on the sequence of COI gene showed that Parabronema belongs to Habronematidae. STF and STR primers based on COI gene were designed, and a 600bp amplicon was amplified from the DNA of . Sensitivity tests showed that specific amplicon could amplified from DNA of ten eggs supplied, and the specific tests showed that the primers have a high specificity to DNA of . It was the first time to report the sequence
