The possible role of haematophagous flies in the incidence of bovine teat papillomatosis

The relationship between the incidence of bovine teat papillomatosis and the activity of haematophagous flies was investigated in Japan. A total of 15,737 flies consisting of 33 species were collected by dry ice-baited mosquito net (DMN) trap and a sweep net from udders of cattle. Simulium aokii (Takahasi) of Simuliidae (black flies) was the predominant species, followed by S. tobetsuense Ono and S. iwatense (Shiraki). Simulium aokii had the highest peak in October, followed by September. Numbers of blood spots from the bites per teat in nulliparous cattle were significantly correlated with numbers of S. aokii collected by DMN trap. Numbers of teats with warts and spots of blood from the bites per teat were significantly more abundant in anterior teats than posterior teats. The average incidence of teat papillomatosis in nulliparous cattle was significantly higher than that in parous cattle, and the highest incidence by month was in May, followed by April. Although bovine papillomavirus (BPV) DNA was not detected in flies examined, the presence of black flies and blood spots from their bites were associated with subsequent high incidence of growing warts. In particular, it would pay to give attention to species such as S. aokii that severely attack udders in the present locality. Further investigations for the detection of BPV DNA from flies parasitizing on teats are needed.