Unrecognized circulation of SAT 1 foot-andmouth disease virus in cattle herds around Queen Elizabeth National Park in Uganda
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
BMC veterinary research
Abstract
Foot-and-mouth disease (FMD) is endemic in Uganda in spite of the control measures used. Various
aspects of the maintenance and circulation of FMD viruses (FMDV) in Uganda are not well understood; these
include the role of the African buffalo (Syncerus caffer) as a reservoir for FMDV. To better understand the
epidemiology of FMD at the livestock-wildlife-interface, samples were collected from young, unvaccinated cattle
from 24 pastoral herds that closely interact with wildlife around Queen Elizabeth National Park in Uganda, and
analysed for evidence of FMDV infection.
Results: In total, 37 (15 %) of 247 serum samples had detectable antibodies against FMDV non-structural proteins
(NSPs) using a pan-serotypic assay. Within these 37 sera, antibody titres ≥ 80 against the structural proteins of
serotypes O, SAT 1, SAT 2 and SAT 3 were detected by ELISA in 5, 7, 4 and 3 samples, respectively, while
neutralizing antibodies were only detected against serotype O in 3 samples. Two FMDV isolates, with identical VP1
coding sequences, were obtained from probang samples from clinically healthy calves from the same herd and are
serotype SAT 1 (topotype IV (EA-I)). Based on the VP1 coding sequences, these viruses are distinct from previous
cattle and buffalo SAT 1 FMDV isolates obtained from the same area (19–30 % nucleotide difference) and from the
vaccine strain (TAN/155/71) used within Uganda (26 % nucleotide difference). Eight herds had only one or a few
animals with antibodies against FMDV NSPs while six herds had more substantial evidence of prior infection with
FMDV. There was no evidence for exposure to FMDV in the other ten herds.
Conclusions: The two identical SAT 1 FMDV VP1 sequences are distinct from former buffalo and cattle isolates
from the same area, thus, transmission between buffalo and cattle was not demonstrated. These new SAT 1 FMDV
isolates differed significantly from the vaccine strain used to control Ugandan FMD outbreaks, indicating a need for
vaccine matching studies. Only six herds had clear serological evidence for exposure to O and SAT 1 FMDV.
Scattered presence of antibodies against FMDV in other herds may be due to the occasional introduction of
animals to the area or maternal antibodies from past infection and/or vaccination.
The evidence for asymptomatic FMDV infection has implications for disease control strategies in the area since this
obstructs early disease detection that is based on clinical signs in FMDV infected animals.
Description
Keywords
Livestock-wildlife interface, Foot-and-mouth disease virus, SAT 1, Young cattle
Citation
Dhikusooka, M. T., Ayebazibwe, C., Namatovu, A., Belsham, G. J., Siegismund, H. R., Wekesa, S. N., ... & Tjørnehøj, K. (2016). Unrecognized circulation of SAT 1 foot-and-mouth disease virus in cattle herds around Queen Elizabeth National Park in Uganda. BMC veterinary research, 12(1), 1-13. DOI 10.1186/s12917-015-0616-1