Confounding of Brucellosis and Blue Tongue in Trans Humane Sheep Flock of Tamilnadu and other Herd Health Impact

This present study was carried out to assess the prevalence of brucellosis and blue tongue in a trans humane sheep flock of Tamil Nadu, India. This Sheep flock had a history of inconsistent abortion, repeat breeder, poor fertility rate and higher prevalence of still birth. Serum samples were collected from sheep by random sampling. Serum samples were subjected to Rose Bengal Plate agglutination test (RBT) and ELISA. The risk factors like pregnancy, abortion, age and sex were correlated to the Brucella seropositivity. This study also assessed for the presence of Bluetongue in aborted sheep. It was found that ELISA could be the choice of test for testing of Brucellosis (with the percentage of 57.14). Clinically healthy rams were found to be with brucellosis seropositivity and posed infertility to ewes. It was observed that in trans humane flocks. Brucellosis and Blue tongue has a confounding phenomenon for ovine abortions.


Introduction
Brucellosis is a bacterial zoonosis caused by microorganisms belonging to Brucella, a genus of gram-negative bacteria that behave as facultative intracellular pathogens of ruminants, suidae, canids, and several wildlife species (OIE, 2008). B melitensis is the foremost etiological agent of brucellosis in sheep and goats. It is also the main agent responsible for human brucellosis known as Malta fever. Abortion and infertility are the predominant clinical signs in small ruminants. B. melitensis infection in sheep and goats has been neglected for long time, because small ruminant production was considered as a represents generally low-income activity practiced by landless farmers and marginalized communities in the developing countries. For these reasons the trans humane farming systems continue to have served disease challenges and pose major hurdles in, the control and eradication of many infections.
The reasons for such high prevalence may also be result of socio cultural factors, which were compounded by the lack of adequate control measures being applied in small ruminant production systems as per the observations of WHO [1]. The Rose Bengal Plate Agglutinations Test (RBT) was developed originally for the diagnosis of bovine brucellosis and despite a scant information on its usage for Sheep and Goat is available, it is also recommended for the screening of B. melitensis infection in small ruminants [2]. In general, indirect ELISA was considered good test for surveillance purposes in which vaccination is no longer used [3]. Infected nonpregnant livestock may not demonstrate clinical signs of infection and this makes the control and prevention more challenging [4].
Bluetongue, which is caused by the Bluetongue virus (BTV) and transmitted by Culicoides spp. Midges, is a major infectious disease of sheep [5,6]. Among the economic losses resulting from BTV infection are abortion and those due to congenital deformities such as hydranencephaly and cerebellar aplasia in calves and lambs [7].
BTV serotypes -10, 11, 13 and 17 are able to cross the placenta and cause fetal infection [8]. Limited information on concurrent

Study Area and Flock Details
This study was carried out during the period between

Choice of Samples
Samples were collected from pregnant non aborted, pregnant aborted, non pregnant ewes and rams. For sample size calculation, expected prevalence of brucellosis was assumed as 20 percent with five percent absolute frequency.

Sampling Methods
Clinical materials like whole blood in EDTA tubes, serum collected in clot activator tubes aseptically and stored in refrigeration until further processing. Simple random sampling method was used for sampling.

Brucellosis Screening
Clinical

Blue Tongue Screening
For blue tongue identification, whole blood in EDTA was collected and subjected to polymerase chain reaction.

Bovine Viral Diarrhoea (BVD) Malignant Cattarhal Fever (MCF) and Chalymidiasis Screening
Serum samples were collected aseptically and analyzed by nested PCR for BVD and MCF. Serology was carried out for Chalymidiasis.

Test Protocols
Rose Bengal plate agglutination (RBT) was carried out as per the OIE prescribed procedure. The recommended steps to improve sensitivity of RBT by using three volumes of serum and  In non pregnant non aborted animals three and one animals were positive for blue tongue and brucellosis respectively ( Table 2).
None of the animals were positive for malignant catarrhal fever, Chalymidiasis and Bovine viral diarrhea.    Even though the goat and cattle reared along with sheep flock, they were not part of this study, however they may had also acted as a cofounder for Brucellosis. Future studies on these aspects will add more information.