Prevalence of besnoitiosis in domestic ruminants in Kenya : a preliminary survey

INTRODUCTION Bovine besnoitiosis was first reported in southern France in 1912 by Besnoit and Robin. Since then it has been reported in Portugal, South Africa, Swaziland, Botswana, Namibia, Zimbabwe, Angola, Kenya, Tanzania, Uganda, Democratic Republic of Congo, Sudan, Cameroon, Nigeria, Israel, former USSR, South Korea and Venezuela. The prevalence is known only in South Africa, Namibia, Zimbabwe, Israel and the former USSR. Caprine besnoitiosis has been reported only in Kenya and Iran. While Bwangamoi et al. stated that goat besnoitiosis was an economically important disease at the Embu, Meru and Isiolo goat breeding stations, its extent in the other goat-producing areas in Kenya is unknown, since no survey has been conducted. This study was undertaken to determine the extent of the occurrence of besnoitiosis in domestic ruminants and whether it warrants attention.


INTRODUCTION
Bovine besnoitiosis was first reported in southern France in 1912 by Besnoit and Robin 12 .Since then it has been reported in Portugal, South Africa, Swaziland, Botswana, Namibia, Zimbabwe, Angola, Kenya, Tanzania, Uganda, Democratic Republic of Congo, Sudan, Cameroon, Nigeria, Israel, former USSR, South Korea and Venezuela 1 .The prevalence is known only in South Africa, Namibia, Zimbabwe, Israel and the former USSR.Caprine besnoitiosis has been reported only in Kenya [3][4][5][6][7]10 and Iran 8 .
While Bwangamoi et al. 7 stated that goat besnoitiosis was an economically important disease at the Embu, Meru and Isiolo goat breeding stations, its extent in the other goat-producing areas in Kenya is unknown, since no survey has been conducted.This study was undertaken to determine the extent of the occurrence of besnoitiosis in domestic ruminants and whether it warrants attention.

MATERIALS AND METHODS
This study was carried out in purposely selected livestock-producing districts in the Coast, North Eastern, Eastern, Central, Rift Valley, Nyanza and Western Provinces of Kenya and the main livestock market in Nairobi.The districts selected in a province were those with the highest numbers of livestock 9 .Cattle, goats and sheep on Government-and privately-owned farms, livestock markets, watering holes, slaughter houses, communal dips and roadsides were examined for the presence of cysts in the eyes as outlined by Bigalke and Naudé 2 .
To confirm the diagnosis, skin biopsies (2 × 1 cm) were aseptically taken on the lateral aspect of the thighs after anaesthetising the area with 2 % lignocaine hydrochloride (Dawa Pharmaceuticals).The wound was closed using a simple interrupted suture pattern (No. 2 nylon, Johnson and Johnson, Kenya) and tetracycline spray applied (Alamycin ® , Norbrook, Kenya).The biopsies were fixed in formalin for 48 hours, sectioned, stained with haematoxylin and eosin and examined microscopically.

Data storage and statistical analysis
Data files of clinical and histopathological results were prepared in DBase IV plus (Ashton-Tate Corporation, Torrance, USA).All statistical analyses were carried out using analysis of variance, sign test and descriptive statistics 15 .

RESULTS
A total of 16 014 cattle, 40 955 goats and 14 818 sheep were examined in 35 districts.
Bovine besnoitiosis was found only in Tana River district in the Coast Province, where 260 (11 %) of 2340 cattle examined had chronic besnoitiosis with the typical elephant skin appearance and many Besnoitia cysts in the different tissues macroscopically and histologically.
Some individual goats flocks in Mandera and Isiolo Districts had prevalence rates as high as 51 %.Examination of goats from Somalia and Ethiopia along Dauwa River that forms the northeastern border of Kenya revealed infection rates between 30 and 51 %.
Unweaned kids (including all kids <4 months of age) in areas categorised as having medium and high caprine besnoitiosis prevalence rates were observed to be infected except in Nairobi.No kids were examined in Garissa, Wajir and Marsabit, as all the goats in these districts were examined in livestock markets.
All the sheep examined were negative for besnoitiosis.

DISCUSSION
The results of this preliminary survey indicated that besnoitiosis is an important disease requiring attention in both cattle and goats.
Bovine besnoitiosis was found in Tana River district, an area bordering the Tsavo East National Park.It is therefore important to determine whether wild animals play a role in its epidemiology.More intensive surveying is also necessary to determine the true incidence of the disease in cattle and wild ungulates, as shortage of funds, lack of security, and inaccessibility of some places, limited the scope of this survey.
Caprine besnoitiosis occurs in a continuous belt extending from the Coast, Eastern, North Eastern, Nairobi and Rift Valley Provinces.It is possible that infection stretches southwards from Kwale into Tanzania, from Mandera northwards into Ethiopia and from Wajir and Garissa eastwards into Somalia.The statement by Bwangamoi 4 that goat besnoitiosis was endemic in Northern and Eastern Kenya, and that only a comprehensive survey could determine the real situation, is supported.
Nairobi has a high prevalence (26 %) compared to the neighbouring districts of Machakos (7 %), Kajiado (1 %) and Kiambu (0).In our opinion this was due to marketing of goats from areas with high prevalence rates, including Mandera, Marsabit, Isiolo, Wajir and Garissa, in Nairobi.The fact that most goats are brought to Nairobi for slaughter may also  explain why unweaned kids in Nairobi were not infected despite the medium prevalence rates.The finding of many infected goats in markets in Nairobi, Garissa, Wajir and Marsabit districts warrants more stringent veterinary restriction of movement of affected animals, as they can spread the disease to areas that do not have the problem.The finding of no infected goats in Tana River, Kilifi and Baringo, all of which border upon districts with besnoitiosis, does not mean absence of the disease.A more comprehensive survey is necessary to ascertain the true situation, as indicated by the fact that Bwangamoi 3 reported goat skins with besnoitiosis from Baringo.
The findings of this study indicate no correlation between the distribution of bovine and caprine besnoitiosis, as no infected cattle were found in any of the districts where goats were infected; moreover, no infected goats could be detected in Tana River district, where bovine besnoitiosis occurred.This confirms the statement by Bwangamoi et al. 7 that cattle raised together with infected goats were apparently free from the disease.These observations, however, need to be confirmed by serological diagnosis.Inoculation of cystozoites orally or ocularly and blood containing endozoites orally to healthy recipients does not result in infection.
Njenga et al. 13,14 demonstrated, by infection experiments and electron microscopy, that caprine besnoitiosis is not caused by Besnoitia besnoiti, which is the aetiological agent of the disease in cattle, but by a different species, which they named B. caprae, as it was hostspecific to the goat and ultrastructurally unique.
The reports on caprine besnoitiosis in Kenya have been scant [3][4][5]7,10,12 . In our iew the reason for this was a lack of awareness about the disease among veterinarians; indeed, many of them were surprised that the disease was so easy to diagnose using the method of searching for scleral-conjunctival cysts 2 .During meat inspection the disease is easily noticed and carcasses condemned, but was often erroneously attributed to Sarcocystis infection.This situation calls for greater emphasis on the disease during training of all cadres of veterinary personnel to enable them to make a prompt and accurate diagnosis and promote control of the disease.
No sheep with besnoitiosis were found in this survey.This was in contrast to a previous report of 3 infected sheep 7 in Kenya and a report of Besnoitia-like infection in lambs in New Zealand 11 .However, neither histopathological nor serological confirmation of infection in sheep has been attempted in Kenya 7 .In our opinion, the reported conjunctival cysts of Besnoitia were most probably bulbo-tarsal glands, which are prominent in sheep and thus easy to confuse with cysts.The fact that there is only 1 other report on besnoitiosis in sheep 11 makes the animal an unlikely host of Besnoitia.

Fig. 1 :
Fig. 1: Distribution in Kenya of goats naturally infected with besnoitiosis.Districts in which infection was found are shaded.