27 March 2019 - In August 2018 FAO published a Focus On entitled “2016–2018 Spread of H5N8 highly pathogenic avian influenza (HPAI) in sub-Saharan Africa: epidemiological and ecological observations”, predicting the potential of H5N8 virus to become established and disperse further within the sub-region. Although reports from African countries decreased over the following months, in February and March 2019 Namibia reported two H5N8 HPAI outbreaks to the World Organisation for Animal Health (OIE), marking the first time the virus was detected in the country. The onset of the first outbreak was observed on 16 January 2019 (confirmed on 2 February 2019) at a breeding site on Halifax Island, affecting a colony of about 7 000 African penguins (Spheniscus demersus). By 5 March 2019, 375 cases had washed ashore near the island, of which 374 died. Dr Jessica Kemper, seabird conservation biologist based in a coastal town in southern Namibia, has been closely monitoring penguin populations for the past 20 years. She believes that these case numbers are underestimated – the island was inaccessible from early December to early January – and many carcasses probably drifted offshore. Photographic evidence shows that the outbreak on Halifax Island area could have started as early as in mid-December 2018.
Importantly, Halifax Island constitutes a roosting and breeding ground for other seabirds, such as kelp gull (Larus dominicanus), crowned cormorant (Microcarbo coronatus), Cape cormorant (Phalacrocorax capensis), greater crested tern (Thalasseus bergii) and Hartlaub's gull (Chroicocephalus hartlaubii). Experts fear that these birds could contract the virus and cause further spread. However, the H5N8 HPAI outbreak seems to be currently limited to adult African penguins and ‘no penguin chicks, nor any other species breeding or roosting on the island seem to be visibly affected’, says Dr Kemper.
Although the origin of H5N8 HPAI introduction into Namibia is still unclear, virus spread from South Africa facilitated by movement of local wild birds is a major possibility, says Professor Celia Abolnik from University of Pretoria’s Department of Production Animals Studies. In June 2017, South Africa confirmed its first H5N8 HPAI occurrence in domestic chickens, and more than 200 outbreaks have been reported since, in both wild and domestic birds. The virus has affected many different species of wild birds, with infection demonstrated by neurological signs and death. Although reports of the disease in South Africa slowed over the second half of 2018, H5N8 HPAI virus is thought to have established itself in the communities of wild Afrotropical aquatic birds, and might periodically spill over to poultry production systems (see FAO Focus On, August 2018). Forthcoming phylogenetic data could potentially confirm a connection between South African H5N8 HPAI viruses and the possible route through which the virus was introduced into Namibia.
Dr Sergei Khomenko, FAO disease ecologist and geographic information system (GIS) specialist said, ‘Nomadic movements of local waterfowl generally occurring in the Southern Africa region are largely driven by seasonal rainfall distribution patterns and anomalies that affect their food and habitat availability. We need to properly analyze conditions preceding the events and couple this information with genetic evidence in order to unravel the puzzling patterns of recent outbreaks ’.
‘Other coastal bird species, like terns, cormorants and gulls, may also move up and down the coast looking for greener pastures to breed’, said Kevin Shaw, ornithologist working for Cape Nature's scientific services in South Africa.
Furthermore, during the period December to February, Palearctic charadrids share habitats with resident species, increasing opportunities for avian influenza viruses to circulate in the communities of coastal birds. Incursion from Namibia or South Africa into unaffected neighbouring countries needs to be considered, particularly for those areas with suitable habitats and conditions for wild birds.
The impact of H5N8 HPAI in wild bird species can be significant as observed previously in South Africa. Eighty-two events affecting 25 different wild bird species were reported to date, leading to more than 6 000 mortalities and putting certain vulnerable species in jeopardy. Wild bird colony protection measures are few and challenging to implement. At a minimum, close monitoring of any unusual behaviour followed by laboratory testing should be put in place. ‘We do our best to test any wild bird that is showing neurological signs or is part of a mass mortality event’, says Dr Laura Roberts, veterinary epidemiologist for the Western Cape Government. ’But in case of disease confirmation, little can be done for the population affected as there is no cure for this virus. Measures we take include limiting human activities at affected sites to avoid further spread and alerting the poultry industry in the vicinity about the presence of the virus.’
While terrestrial poultry and ducklings have exhibited high susceptibility to the H5N8 HPAI virus, it is important to consider that infection is likely asymptomatic in wild afro-tropical ducks and may cause sporadic, and not necessarily mass mortalities in other wild birds. Over the coming months, countries in the Southern African region, in particular Mozambique, Malawi, Zimbabwe, and to a lesser degree Zambia, Angola and the Democratic Republic of the Congo, should remain on high alert for virus introduction and follow up on any mortalities observed in wild birds or terrestrial poultry.
To date no human infection with H5N8 isolates has been reported.