Published at: XX International Congress of Mediterranean Federation of Health and Production of Ruminants, 19-22 February (2013), Assiut University, Egypt
Oestrosis is a worldwide myiasis caused by larvae of the fly, Oestrus ovis, which are obligate parasites of the nasal and sinus cavities of sheep and goats, especially in Mediterranean countries. The aims of this study were to determine the immunogenicity of ESP products of O. ovis third larvae (L3) against development of naturally infested larvae in excretory- secretory products (ESP) vaccinated and control lambs. For these purposes, six Baladi lambs of six months old, maintained indoors from birth to their necropsy, were randomly allocated into two groups
(4 vaccinated and 2 controls). In the vaccinated group each animal received two S/C injections of ESP in the neck, 4 weeks apart, initially in Freund’s complete adjuvant and then in Freund’s incomplete adjuvant . The total amount of ESP injected into each sheep was 1.5 mg of protein (1 mg in the first injection and 0.5 mg in the second). In the control group, lambs received two S/C injections of RPMI-1640 medium with Freund’s complete then incomplete adjuvants. Challenge tests were carried out twice, on day 45 through natural infestations, which had been done for the first time, using 9 adult flies (2 males and 7 females) and day 58 using 7 adult flies (3 males and 4 females) after primary immunization (namely 15 days and 28 days after the second immunization). On the 5th week post second challenge, all animals were slaughtered and larvae were collected from the septal, turbinate, ethmoid mucosae and the sinus cavities, counted and their stages were identified. Results indicated that L3 ESP antigenic extract of O. ovis adversely affected survival rates of 1st and 2nd larval instars (L1 and L2), 38.46% and 33.33% versus 61.54% and 66.66% in the control group, respectively, whereas the total survival rates were 38.18% and 61.18% in the vaccinated and control groups, respectively. The mean number of larvae/ sheep in the vaccinated group was 4.66+2.03, while that of the control group was 17+2.00. The total larval reduction % was 72.54% and those of L1 and L2 were 72.94% and 67%, respectively. It was concluded that L3 ESP immunization of sheep reduce parasitic burden, protected against larval survival and provided an inhibitory effect on larval growth. Such curtail of the life cycle of O. ovis will reflect on animal’s health and production and increase the national income.
Keywords: Oestrus ovis, sheep, excretory- secretory products, immunization, naturel challenge