12 February 2010

3 minute read

The Panel on Animal Health and Welfare has delivered a scientific statement on Bovine Besnoitiosis, which says it should be considered an emergin disease in the EU.

Many aspects of the epidemiology of bovine besnoitiosis remain uncertain including, prevalence and incidence of infection and disease in endemic areas, routes of transmission and risk-factors associated to infection and disease. It is suspected that B. besnoiti has a heteroxenous life cycle. The definitive host (DH) has not been identified.

The relationship between B. besnoiti and other Besnoitia spp. from ungulates remains to be elucidated. Horizontal direct and indirect transmission seems to be responsible for the spread of the disease. Arthropods such as horseflies and deer flies may play a role by transmitting B. besnoiti mechanically from chronically or asymptomatic infected cattle. Wild ruminants and probably rodents should not be disregarded as reservoirs of the parasite.

The infection can cause serious adverse effects both during the acute and chronic phases that could compromise animal welfare. Bovine besnoitiosis has two distinct sequential clinical stages, namely, the acute anasarca stage, which is mainly associated with proliferation of endozoites in blood vessels, and the chronic scleroderma stage which is mainly associated with cyst formation. The severity of the disease may vary between mild and severe with possible deaths in seriously affected animals. Many infected animals remain asymptomatic and the only sign of the disease is the presence of cysts in sclera conjunctiva and/or vulval area in cows. A number of diagnostic tests such as cytology, histopathology, serology and PCR testing are available. There are not any effective drugs or vaccines available in Europe at present.

The Animal Health and Welfare Panel recommends that epidemiological investigations in endemic areas in Europe are necessary to elucidate the importance of infected animals and the routes of transmission. In this context, relevance of direct transmission through direct contact during natural mating should be evaluated. Moreover, entomological studies can be used to evaluate e.g. the abundance of stable flies (Stomoxys calcitrans) or tabanids during such surveys, addressing the potential role of these biting flies in transmission.

Further studies are necessary to elucidate the role of wild ruminants and rodents as putative reservoirs of the parasite. The existence of a definitive host and its role in the epidemiology of bovine besnoitiosis should be studied. Furthermore, the relationship between B. besnoiti and other Besnoitia spp. isolated from ungulates (B. tarandii and B. caprae) should be investigated to assess the risk of infection for domesticated ruminants.Diagnostic tools need to be further developed and standardised to address unanswered questions related to the epidemiology and clinical progression of the disease. Appropriate measures and strategies to control of Besnoitiosis need to be investigated using the available epidemiological information.

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