FLOCK-BASED SURVEILLANCE FOR LOW PATHOGENIC AVIAN INFLUENZA VIRUS IN COMMERCIAL BREEDERS AND LAYERS, SOUTHWEST NIGERIA.

BACKGROUND: Flock surveillance systems for avian influenza (AI) virus play a critical role in countries where vaccination is not practiced so as to establish the epidemiological characteristics of AI needed for the development of prevention and control strategies in such countries. MATERIALS AND METHODS: As part of routine AI monitoring in southwest Nigeria, a competitive ELISA was used for detecting influenza A virus antibodies in the sera of 461 commercial breeder and layer birds obtained from different flocks in Oyo State, Nigeria while haemagglutination inhibiting antibodies against low pathogenic AI viruses (LPAIVs) were detected using H5N2, H7N7 and H9N2 subtype-specific antigens. Suspensions prepared from cloacal swabs were tested for AI virus RNA using reverse transcriptase-polymerase chain reaction. RESULTS: Results showed that influenza A virus antibody prevalence was 12.8% and 9.3% for breeders and layers, respectively while HI assay revealed 22.0%, 2.0% and 78.0% prevalence of LPAIV H5N2, H7N7 and H9N2 antibodies respectively. All cloacal swab suspensions were negative for AIV RNA. CONCLUSION: Since LPAI infections result in decreased or complete cessation of egg production in breeder and layer birds, increased infection severity due to co-infection with other poultry viruses have occasionally been transmitted to humans, the detection of LPAIV H5N2, H7N7 and H9N2 antibodies in these birds is of both economic and public health significance. These findings underscore the need for continuous flock monitoring as part of early warning measure to facilitate rapid detection and sustainable control of AI in Nigerian poultry.

Serological Investigation of Akabane Virus Infection in Cattle and Sheep in Nigeria.

Akabane virus (AKAV) is recognized as an important pathogen that causes abortions and congenital malformations in ruminants. However, it has not received adequate attention in Nigeria. Therefore, in investigating this disease, serum samples from 184 (abattoir and farm) head of cattle and 184 intensively reared sheep from two states in southwest Nigeria were screened for antibodies against AKAV using enzyme-linked immunosorbent assay. An overall seropositivity of 70.1% (129/184) was obtained with antibodies being detectable in 73.8% of abattoir (trade) cattle and 40.0% in farm cattle, while 4.3% (8/184) seropositivity was observed in sheep. All the age groups of cattle tested had seropositive animals, 0-1 year (1/7, 14.3%), 2-3 years (17/34, 50.0%), 4-5 years (92/121, 76.0%), and >5 years (19/22, 86.4%), while in sheep only the age groups of 2-3 and 4-5 years showed seropositivity of 4.1% (4/97) and 8.2% (4/49), respectively. The detection of antibody-positive animals among unvaccinated cattle and sheep provides evidence of AKAV infection in Nigeria. These findings call for continuous monitoring of the disease among ruminants in order to ascertain the actual burden and increase awareness of the disease. This will facilitate early detection and aid the development of appropriate control measures against the disease in Nigeria.

Serological Survey for Avian Influenza in Turkeys in Three States of Southwest Nigeria.

Since the first outbreak of avian influenza (AI) in Nigeria in 2006, there has been continuous monitoring of the disease in chickens with little attention given to turkeys. As part of on-going surveillance for AI in southwest Nigeria, we used a competitive ELISA to detect anti-AI virus antibodies in 520 turkey sera obtained from poultry farms in Oyo, Osun, and Ondo states while haemagglutination inhibiting antibodies against low pathogenic AI viruses (LPAIVs) were detected using H3N8 and H5N2 subtype-specific antigens. The overall seroprevalence obtained by ELISA was 4.4% (23/520). Of the 23 ELISA-positive samples, 18 were positive for anti-AIV H3N8 antibodies only and four were positive for both anti-AIV H3N8 and H5N2 antibodies indicating a mixed infection, while five were negative for antibodies to either of the two AIV subtypes. Considering that turkeys have been implicated as a mixing vessel for generating influenza virus reassortants of human and avian origin, the detection of antibodies to LPAIV H3N8 and H5N2 in these turkeys is of public health concern. We advocate further studies to determine the potential role of turkeys in the zoonotic transmission of AIVs in Nigeria. Additionally, the practice of rearing turkeys with chickens should be discouraged.

Occurrence of Newcastle Disease and Infectious Bursal Disease Virus Antibodies in Double-Spurred Francolins in Nigeria.

The double-spurred francolin Francolinus bicalcaratus has been identified as a good candidate for future domestication due to the universal acceptability of its meat and its adaptability to anthropogenically altered environments. Therefore, in investigating the diseases to which they are susceptible, serum samples from 56 francolins in a major live-bird market (LBM) in Ibadan, southwestern Nigeria, were screened for antibodies against Newcastle disease (ND) and infectious bursal disease (IBD) viruses. Haemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) revealed 25.0% and 35.7% prevalence of ND virus (NDV) antibodies, respectively, while 5.4% and 57.1% prevalence of IBD virus (IBDV) antibodies was detected by agar gel precipitation test (AGPT) and ELISA, respectively. This first report on the occurrence of NDV and IBDV antibodies in apparently healthy, unvaccinated double-spurred francolins from a LBM suggests that they were subclinically infected with either field or vaccine viruses and could thus serve as possible reservoirs of these viruses to domestic poultry. Furthermore, if they are to be domesticated for intensive rearing, a vaccination plan including ND and IBD should be developed and implemented.