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International Society for Infectious Diseases
Date: Mon 15 Feb 2010 [accessed]
Source: Question number: EFSA-Q-2009-00879, adopted 28 Jan 2010,
published 11 Feb 2010 [edited]
Bovine Besnoitiosis: An emerging disease in Europe
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Summary
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The European Food Safety Authority (EFSA) asked the Panel on Animal
Health and Welfare to deliver a scientific statement on bovine
besnoitiosis.
Recent epidemiological data confirm an increased number of cases and
geographic expansion of besnoitiosis in cattle herds in some EU MS
[member states], therefore bovine besnoitiosis [BB] should be
considered an emerging disease in the EU. Many aspects of the
epidemiology of BB remain uncertain, including prevalence and
incidence of infection and disease in endemic areas, routes of
transmission and risk factors associated with infection and disease.
It is suspected that _Besnoitia besnoiti_ has a heteroxenous life
cycle [having more than one obligatory host]. 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. BB has 2
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 no 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 BB 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 standardized to address unanswered questions related to the
epidemiology and clinical progression of the disease. Appropriate
measures and strategies to control Besnoitiosis need to be
investigated using the available epidemiological information.
--
Communicated by:
Sabine Zentis
Gut Laach 52385 Nideggen, Germany
[_B besnoiti_ has been reported from southern Europe, Africa, Asia,
and South America; it has not been reported in cattle in North
America. These Toxoplasma-like organisms multiply in endothelial,
histiocytic, and other cells, causing changes in the skin, subcutis,
blood vessels, mucous membranes, and other tissues in cattle.
Live-attenuated vaccines have been developed; they are produced and
are applied on a limited scale in selected animal groups such as
imported bulls and breeding cattle in South Africa and Israel.
The full EFSA document (EFSA Journal 2010; 8(2):1499; 15 pages)
includes the following chapters:
1. Introduction
2. Geographical distribution of Bovine Besnoitiosis
3. Aetiology and life cycle
4. Epidemiology
4.1. Prevalence
4.2. Transmission
4.3. Risk factors
5. Pathogenesis, clinical signs and lesions
6. Diagnosis and control
7. Economic and welfare impact
Conclusions and recommendations
References.
Subscribers are encouraged to access the paper at the above URL. - Mod.AS]
[Photo of typical "elephant skin" of an infected cow:
- Mod.JW]
.............................................arn/msp/jw
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