Epidemiological investigation of bovine blindness syndrome in local and improved herds in Mkinga district of Tanzania.

Aim: A demand-driven epidemiological field and laboratory investigation of a 'bovine blindness syndrome, BBS' was conducted in Mkinga district of Tanzania during the period of June through August, 2009. Materials and methods: Participatory epidemiological (PE) methods including focus group discussion (FGD), proportional piling and matrix scoring were used to characterize clinical signs, disease impact and risk factors for BBS as perceived by livestock keepers. PE investigation was complimented by microbiological culture of ocular discharges (n = 96 swab samples), clinical examination of animals and entomological investigation of the 'butterfly insects like' that were suspected by livestock keepers to be associated with BBS. Results: Matrix scoring showed moderate to good agreement between informant groups on the clinical signs, risk factors, disease impact and occurrence which coincides with rainy season. Clinical examination of cattle (n=177) from six villages revealed that 72 (40.7%) presented discharges from eyes, of which the majority had serous discharges (n=35; 48.6%) while muco-purulent and dried discharges were recorded in 19.2% and 32.2% of the animals, respectively. Of the 37 cattle that were found to be blind (based on obstacle test), most were affected in the right eye and the prevalence of blindness was significantly higher in indigenous than in cross-bred cattle (26.1% vs 5.4%, p=0.0027). Entomological examination of insect specimens identified the suspected 'butterfly insects' to be moths that belong to the species Arcyophora longivalvis, reported to serve as mechanical carriers for Moraxella bovis, a bacterium that causes Infectious Bovine Keratoconjuctivitis (IBK or Pinkeye) which among others, it causes blindness in cattle. M. boviswas isolated from 83.7% of 96 samples cultured. Conclusion: It is concluded that blindness in cattle in the area under study district was due to M. bovis infection. To the best of our knowledge, this is the first study in East Africa which has associated A. longivalvis moths with transmission of IBK. Appropriate disease prevention and control measures for pinkeye should be adopted in order to safeguard animal health in Mkinga. [ABSTRACT FROM AUTHOR]