Seroprevalence of bluetongue in sheep and goats in Egypt

Aim: The study was undertaken to understand the epidemiological status of bluetongue infection in Egypt. Materials and Methods: Serum samples were collected from clinically healthy as well as suspected sheep and goats. Samples were collected during the vector breeding season from September to November 2010, from 14 Egyptian governorates which represent different geographical regions of Egypt, and were tested by Agar Gel Immuno-precipitation Test (AGPT). Results: Out of total 1293 animal serum samples (sheep-1028 and goats-265), 17.5% of sheep and 14.7% of goats serum samples were found positive. The overall prevalence of anti-BT antibodies in different governorates was 16.9%. The highest prevalence of bluetongue group specific antibodies was detected in Beni-Suef, Giza, and Al Sharqia governorates (13.2%). The results indicate that there is a necessity to run further studies to identify the negative governorates. In addition, there is a lack in information regarding the BTV serotypes in Egypt. Conclusion: This study reflected high seroprevalence of bluetongue infection in sheep than goats. The results indicated that further studies are needed to identify the vectors from different agro-climatic zones, in addition, the BTV serotypes that are circulating in Egypt.


Introduction
the world, the latitudinal band is between 40°N and 35°S where Culicoides midges are extremely abundant Bluetongue (BT) is an infectious non contagious [9].The first confirmed outbreak of bluetongue disease insect-born viral disease of sheep.The causative agent was reported in island of Cyprus [10].BTV has not is a double-stranded RNA virus (genus Orbivirus, been identified in Antarctica continent until now [8].family Reoviridae) which infects domesticated and Clinical signs of the disease are generally clear in wild ruminants [1].24 distinct bluetongue virus (BTV) sheep and some wild ruminants, but are uncommon in serotypes have been identified for decades.All of them goats and cattle.However special serotypes like serotype are capable to initiate the disease in ruminants.
8 have clinically affected mainly cattle in Europe.However, 2 new bluetongue virus serotypes, BTV-25 Symptoms range from subclinical to acute febrile (Toggenburg orbivirus, from Switzerland) and BTV-26 response.It is characterized by inflammation and (from Kuwait), were recently identified in goat and congestion leading to facial edema and hemorrhages, sheep respectively [2].ulceration of the mucous membranes.solution (0.9% NaCl in distilled water).Agarose Within the examined 1293 sheep and goats serum isotonic saline solution was poured onto Petri dishes to samples originated from 14 governorates, by AGPT for form a layer of 2.5 mm thickness.Then the plates were presence of BT group specific antibodies, the over all allowed to stand open on a horizontal bench for antibody prevalence was 16.7%.It demonstrates the cooling.Seven well patterns 6 mm in diameter and 2.5 high prevalence of anti-BTV agar gel precipitating mm a part were punched in each plate.The antigen was antibodies in sheep and goats in different governorates added into the central well while the directed well to the that represent different geographical areas in the north was filled to the brim with 50-60 µl of control country.It supports the results, which were previously positive serum.The remaining 5 wells were designed obtained by Hafez and Ozawa [12].for the serum to be tested.The plates were incubated at The average of BTV antibody prevalence was room temperature for 48 hours.
slightly higher in sheep (17.5%) than in goats (14.7%)Test plates were held at room temperature in a as shown in Table 1.The susceptibility of goats to BT humidified chamber for 24 hours.Serum samples were virus was variable, but generally goats were resistant to recorded as positive when the precipitin lines formed natural infections [19].lines of identity with the positive-control serum or Some governorates like Suiz, Damietta, and when they caused the positive control precipitin line to Dakahlia showed zero percentage of seropositivity in bend toward the antigen well (weak positives).their samples.Like these governorates, more epidemiological data is required and further examinations of

Results and Discussion
larger number of animals are recommended for complete According to the list of International Office of conclusion about these areas.Other governorates showed Epizootics, the Bluetongue disease is classified as a low percentage of seropositivity in their samples communicable and a wide spreading worldwide (0.1%-1.1%).On the other hand, high percentage of disease [17].Bluetongue is of an economical importance seropositivity in serum samples is recorded in Benibecause it causes deleterious effects on the reproductive Suef, Al Sharqia and Giza (6.5%, 3.8% and 2.9% function such as abortions, early embryonic loss and respectively) although the three governorates are apart congenital malformations in the affected ruminants and do not share any borders.
[18].This study was carried out to throw a light on the The animal susceptibility to the virus infection is situation of this disease in Egyptian animal population attributed to multiple epidemiological factors such as through evaluating its seroprevalence, that would help competence, distribution of the vector and feeding decision makers and stakeholders.habits of the vector.Animal age also plays a role where The serological data of BTV is poorly defined in older animals tend to be more susceptible than younger Egypt and limited to the results of a serological survey ones.The severity of clinical signs seems to vary that was carried out by Hafez and Ozawa [12].They according to the animal breed and the infecting reported that BTV antibodies were distributed nearly serotype of the virus [20].all over the country (9%) and precipitating antibodies Because the AGPT detects BTV group specific in ovine sera collected from free and endemic areas antibodies and hence it is not serotype-specific and less were about 37 %.
sensitive than ELISA, in governorates that show low

Figure- 2 .
Figure-2.Results of AGPT for detection of BTV specific antibodies in sheep and goats sera collected from different governorates in Egypt.

immuno-precipitation test (AGPT): A Serum samples collected for detection of BTV group modification
) during the vector breeding In this paper we studied the prevalence of BTV group season from September to November 2010 and tested specific antibody in 14 governorates of the Upper and by the AGPT (Table-2, Figure-2).Lower Egypt, using Agar Gel Immuno-precipitation Blood samples: 5 ml of blood was collected aseptically Test (AGPT) in randomly collected serum samples from jugular vein of each animal using anticoagulant from sheep and goats.free vacutainer tubes and transported on ice to the of the AGIDT was used to detect BTV specific antibodies by AGPT: A total of 1293 sheep and group-specific antibodies according to Taylor and goats serum samples were collected from suspected McCausland [16].Serum samples were tested against and clinically healthy sheep (1028) and goats (265) BTV antigen (Bluetongue AGID antigen, was obtained from 14 governorates of the Upper and Lower Egypt from Pirbright England) in agarose isotonic saline representing different geographical regions of the ].The distribution of bluetongue is bluetongue virus is endemic[14].effectivelyrestrictedto a latitudinal band around the However, variation in the pathogenesis of strains world between 50°N and 30°S in America.In the rest of of bluetongue virus has been reported among some serotypes[15].There is a prerequisite for full epidemiological understanding of the bluetongue status of any country, pathogenicity of the serotypes present, isolation and characterization of these viruses.country (Figure-1, Table-1Agar gel

Table - 1
. The governorates names and their key numbers

Table -
2. AGPT for detection of BTV antibodies in the serum samples.