JCPZ confirms avian botulism likely cause of Zoo Lake bird deaths

Johannesburg City Parks and Zoo stated it was still working with the municipality to establish any links to contamination caused by humans. A veterinary report has stated that avian botulism is the likely cause of the recent bird deaths at Zoo Lake; however, laboratory tests are still pending. At least 20 waterbirds were found dead in and around Zoo Lake earlier in November, with a further 74 bird carcasses found this week. Johannesburg City Parks and Zoo (JCPZ) said the human health risk is low, but the affected birds could carry other pathogens and should be avoided by the public. JCPZ asked visitors to the popular Zoo Lake recreation site not to feed the birds in the area, especially bread and similar foods that could accumulate and decay in the lake. “Avoid touching, collecting or transporting sick or dead birds, keep children and pets away from carcasses and the affected water and report all sightings of ill of dead birds to JCPZ,” the entity stated. No avian influenza found While traces of avian botulism were found, the Onderstepoort Veterinary Hospital confirmed tests were negative for avian influenza. The author of the veterinary report, Dr Dewald Keet, said the previous incidents and the lake’s environmental conditions had correctly pointed to avian botulism. “Prompt carcass removal is the most effective immediate intervention to break the carcass-maggot cycle and limit further losses. “Sustained attention to water quality and accumulated organic matter is also essential,” stated Keet. JPCZ said avian botulism resulted from birds ingesting a toxin produced by clostridium botulinum bacteria. “Warm to hot weather can exacerbate conditions by increasing water temperatures, accelerating the decomposition of organic material and reducing dissolved oxygen. “Together with stagnant water and accumulated organic matter, these conditions can favour outbreaks,” JPCZ stated. The municipal entity stated that the carcasses found this week had been taken to the Johannesburg Zoo for incineration. No swimming or fishing The botulism neurotoxin causes muscle weakness and paralysis, leaving the birds unable to fly, feed or keep their heads above water. JCPZ stressed that while the risk to humans was low, the water in the lake was unsafe for pets, swimming or fishing. The entity said that claims of human contamination required additional investigation, but that no “direct causal link between a particular spill and the bird deaths” had yet been established. “Our teams are recovering carcasses and transporting them to the Johannesburg Zoo for incineration, while working with the City’s EISD to address the environmental conditions contributing to this problem. “We ask residents to support these efforts by avoiding feeding the birds, keeping pets on a leash at all times, staying a safe distance away from the water and reporting affected wildlife promptly,” JCPZ managing director Thanduxolo Mendrew stated.