Effect of vaccination on cattle herds previously exposed to foot and mouth disease in Cameroon

Authors: BERTRAM, MIRANDA - Oak Ridge Institute For Science And Education (ORISE); DELGADO, AMY - Animal And Plant Health Inspection Service (APHIS); Pauszek, Steven; Smoliga, George; BRITO, BARBARA - Oak Ridge Institute For Science And Education (ORISE); STENFELDT, CAROLINA - University Of Minnesota; Hartwig, Ethan; DICKMU-JUMBO, SIMON - Lanavet; ABDOULMOUMINI, MAMOUDOU - The University Of Ngaoundere; ABONA OLIVIA, AMBA - The University Of Ngaoundere; SALHINE, ROBERT - The University Of Ngaoundere; Rodriguez, Luis; GERABED, REBECCA - The Ohio State University; Arzt, Jonathan

Submitted to: Preventive Veterinary Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2018
Publication Date: 4/11/2018
Citation: Bertram, M.R., Delgado, A., Pauszek, S.J., Smoliga, G.R., Brito, B.P., Stenfeldt, C., Hartwig, E.J., Dickmu-Jumbo, S., Abdoulmoumini, M., Abona Olivia, A., Salhine, R., Rodriguez, L.L., Gerabed, R., Arzt, J. 2018. Effect of vaccination on cattle herds previously exposed to foot and mouth disease in Cameroon. Preventive Veterinary Medicine. 155:1-10. https://doi.org/10.1016/j.prevetmed.2018.04.003.
DOI: https://doi.org/10.1016/j.prevetmed.2018.04.003

Interpretive Summary: Foot and mouth disease (FMD), caused by FMD virus (FMDV), is an important livestock disease that causes substantial animal health problems and economic losses in many countries in Africa and Asia, where the disease is endemic. Vaccination can help to control FMD, however vaccinated animals may become infected without getting sick. Additionally, the presence of different types of FMDV in different regions requires vaccines to be tailored to each region, and countries should check how well a particular vaccine works in that country. Cameroon recently started vaccinating cattle against FMDV, and the purpose of this study was to characterize vaccine performance under natural conditions in cattle previously exposed to FMDV in Cameroon. Vaccinated cattle and unvaccinated controls were monitored for one year, and samples were collected periodically to test for FMDV. Over half of the animals had been infected with FMDV prior to the study, and nearly all the remaining animals were infected during the study. However, only a small number of unvaccinated cattle were observed to be sick during the study. This study suggests vaccination of herds previously exposed to FMDV may help limit clinical signs and reduce economic losses caused by within-herd spread of FMDV. These findings have implications for FMDV control in Cameroon and other regions where FMDV is endemic.

Technical Abstract: Foot and mouth disease (FMD), caused by FMD virus (FMDV), is one of the most contagious and economically important livestock diseases worldwide. Four serotypes of FMDV are endemic in Cameroon (O, A, SAT1, SAT2), and a trivalent inactivated vaccine against the three most common serotypes (O, A, SAT2) was recently introduced. The objective of this study was to characterize vaccine performance in cattle under natural hyper-endemic conditions in the Adamawa region of Cameroon. Vaccinated cattle (n=50) and controls (n=100) were monitored by serum and oropharyngeal fluid (OPF) sample collection through a 12 month period. Samples were screened for the presence of anti-FMDV non-structural protein (NSP) antibodies by ELISA (serum) and FMDV RNA by rRT-PCR (OPF). Although viral RNA was found in 42 (28%) animals overall, and anti-NSP seroprevalence was 85% (n=120) at the end of the study, clinical signs of FMD were observed only in 6 unvaccinated animals across two outbreaks. Viral sequence analysis indicated that subclinical infections of FMDV serotypes O and A were present within the study herds during the study period. Overall anti-NSP seroprevalence increased from 59.3% to 85.8% during the study, with no significant effect associated with vaccination. Among animals that were seronegative at the start of the study (n=61), the incidence risk of anti-NSP antibody seroconversion during the study was 91.4%, and the incidence rate was 0.006 per animal-day at risk. There was no association between vaccination status and seroconversion or prevalence of FMDV RNA in OPF. Younger cattle had higher odds of detection of FMDV RNA in OPF, but older animals were more likely to be seropositive. This study suggests vaccination of herds previously exposed to FMDV may help limit clinical signs and reduce economic losses caused by within-herd spread of FMDV. These findings have implications for FMDV control in Cameroon and other hyper-endemic regions.