Published at: XX International Congress of Mediterranean Federation of Health and Production of Ruminants, 19-22 February (2013), Assiut University, Egypt
The sheep nasal fly, Oestrus ovis, is an obligate parasite of the nasal cavities and adjoining sinuses of sheep and goat. Oestrosis impairs the wellbeing and performance of the hosts, affecting growth, wool and milk production.A study was carried out to estimate the prevalence, larval burden and risk factors of ovine oestrosis from June 2011 to April 2012 at El-Basateen abattoir, Cairo, Egypt. The larval stages of O. ovis were found in 360 of 3132 sheep heads (11.49%). Sheep of all ages were vulnerable to infestation and especially when they are 1-2 years old (12.78%). Seidy breed was more infested (78.57%) than other breeds (14.43%, 13.33% and 10.71% for Dernawy, Ossimy and Baladi, respectively). In general, there was no significant effect (P ≤ 0.05) of age and breed on larval burden. The highest infestation rates had three peaks, in October (23.42%) followed by December (18.07%) and May (18.29%). The lowest peak of infestation (5.95%) was recorded in February. A higher rate of seasonal prevalence was recorded in autumn (17.91 %) followed by spring (13.92%), while the lowest prevalence was recorded in winter (7.85%). A total of 2008 larvae [264 L1 (13.14%), 755 L2 (37.59%), and 989 L3 (49.25%)] were collected from 360 infested animals. Larval burden of L2 and L3 were always present during this twelve month study, while L1 were not seen during December. The lowest peaks of infestations with L2 (15.51%) and L3 (28.90%) were observed in December and June, respectively. On the other hand, the highest peaks for L1 (20.10%), L2 (53.17%), and L3 (84.48%) were recorded in September, June, and December, respectively. The seasonal prevalences were observed in summer and autumn for L1 and L2 as well as in winter and spring for L3. Seasonal distribution of larval burden and the number of larvae per sheep (L/S) were 606 and 3.03}0.16 in spring; 509 and 2.22}0.09 in summer, 567 and 2.96}0.13 in autumn; and 326 and 3.16}0.22 in winter, respectively. The overall L/S and range of recovered larvae were 2.77}0.07 and (1-20); whereas those of L1, L2 and L3 were 1.83}0.08 and (1-6); 2.75}0.10 and (1-10); and 3.23}0.13 and (1-13), respectively. It was concluded that oestrosis is common in Egyptian sheep and the prevalence is higher in young than adult rams and in Seidy sheep other breeds. Sheep nose color could be considered as a risk factor of the disease. The relative percentages of L3 indicated
a year-round development and flies are present with at least three generations per year. This epidemiological status implied that animals have to be treated frequently all the year round in order to reduce the prevalence, clinical signs, economic losses, and reinfestations with oestrosis.
Keywords: Survey; Oestrus ovis; prevalence; sheep; Egypt; larval burden