Development of a quadrivalent foot-and-mouth disease vaccine candidate for use in East Africa.

Foot-and-mouth disease (FMD) is a highly contagious viral disease of livestock which is prevalent across Africa, the Middle East, Asia, and South America where it has a severe economic impact on the agriculture industry. Vaccination with inactivated viral vaccines is used as the main control measure in these endemic regions of the world, however the presence of multiple serotypes, subtypes, and the continual emergence of new, antigenically divergent strains limits its effectiveness. East Africa (EA) has been identified as a region that would particularly benefit from updated FMD vaccines, since those currently in use contain older strains which do not provide good protection against contemporary strains. Four serotypes are currently circulating in EA, necessitating the development of a quadrivalent vaccine containing representative strains of each serotype. A key consideration in the selection of vaccine strains is the stability of the virus particle, since the capsids readily dissociate on exposure to elevated temperatures, but only intact capsids induce protective immunity to FMD. Therefore, with a view to producing a more stable, updated quadrivalent vaccine for EA, we recently screened a panel of foot-and-mouth disease virus (FMDV) isolates from the region to select strains with naturally higher thermostabilities and confirmed their immunogenicity in cattle. Herein we describe the formulation and serological assessment of wild-type and recombinant quadrivalent vaccine candidates comprising these stable strains, and demonstrate that both vaccines generate high neutralising antibody titres against the homologous strains and also to heterologous strains from EA. Importantly, the vaccine passed the criteria set by the AgResults vaccine challenge project and offers good cross-protection against a panel of regional FMDV strains.

DIAGNOSIS OF ORF IN WEST AFRICAN DWARF GOATS IN UYO, AKWA IBOM STATE, NIGERIA.

BACKGROUND: Sixty (60) male West African Dwarf goats were reported with clinical signs of enlarged lymph nodes, scabs on the mouth, nose and ears. Two of the goats died and post mortem examination reveals enlarged submandibular lymph nodes and vesicular lesions on the tongue. Clinical diagnosis of Orf has been reported in Nigeria but this report is the confirmatory diagnosis of Orf in a suspected outbreak in an experimental farm in Uyo, Akwa Ibom State, Nigeria using molecular techniques. MATERIALS AND METHODS: Scabs, spleen and lymph node samples from goats suspected to have died from Orf were collected, transported on ice to the laboratory and homogenized. The DNA was extracted using QIAmp DNA minikit (Qiagen) according to the manufacturer's instructions. Orf virus (ORFV) was amplified using published ORFVspecific primers by PCR. RESULTS: Morbidity and mortality were 100% and 3.3% respectively, while ORFV was detected by PCR. Diagnosis of Orf was confirmed based on clinical signs of enlarged lymph nodes, scabs on the mouth, nose and ears, necropsy findings of enlarged submandibular lymph nodes and vesicular lesions on the tongue and PCR results. CONCLUSION: This may be the first report of molecular diagnosis of Orf in Nigeria. The 100% morbidity and 3.3% mortality rate is higher than previously reported thus Orf is becoming of greater economic importance than previously thought. It is therefore recommended that routine laboratory diagnosis of Orf be carried nationwide to determine the prevalence of Orf in Nigeria.