Avian pox in Swainson’s francolin in South Africa

Field trips were undertaken in South Africa from 1997–2001 to determine the prevalence of poxvirus infection in Swainson’s francolin, Francolinus swainsonii. In total, 200 specimens were trapped or shot and examined for external lesions. Selected tissues from three dead specimens were removed for histopathological examination. Eighty-eight (44%) of 200 specimens revealed lesions, the highest compared to other wild bird populations. Other species such as ducks, doves, pigeons, helmeted guinea fowl (Numida meleagris) and other francolin species were also examined for similar lesions. Only one specimen (Coqui francolin, F. coqui) of 673 showed similar signs. This absence in other species suggests that Swainson’s francolin can serve as an indicator species for certain poxviruses in a local or regional context. Swainson’s francolin on the highveld showed a much higher prevalence of poxvirus infection than those in the bushveld. It is suggested that extreme cold conditions and lack of adequate food and cover during winter cause a stressful bottleneck. Swainson’s francolin are dispersed in summer but converge in winter into groups, facilitating the spread of the virus between individuals.