Avian flu: What farmers should do

This week, the ministries of agriculture and health issued an alert about an avian flu outbreak in Wakiso, Kalangala and Masaka districts. This followed reports of several migratory birds found dead on the shores of Lake Victoria in these areas.

In his statement, Agriculture minister Vincent Ssempijja revealed that specimens taken from white-winged tern found in Lutembe, Wakiso District, turned positive for the Highly Pathogenic Avian Influenza (HPAI).
Dr Halid Kirunda, the director of Naro’s Mbarara zonal research institute, who is an expert in avian influenza, explains that there had been some farmers had previously reported deaths of their birds but did not know AI virus was the cause.

The current outbreak is of the highly pathogenic (disease causing) virus which has not only occurred in Uganda but in Africa.

Egypt is one of the countries considered endemic to bird flu and hence a threat to other countries, especially those with which it shares a global wild bird migratory route such as Uganda.
Avian Influenza genetic material has been detected in free-living water birds, domestic ducks, turkeys, chickens and pigs.
Specifically, the H5 strain was detected in 45 birds out of 4,052 positive samples in a study carried out between 2010 and 2014.

In Uganda, genetic cause and antibodies against AI viruses were detected in wild and domestic birds as well as pigs mainly in central Uganda.
It is prevalent in March and November, January, September and December; more so in wet than dry seasons.
Farmers should restrict movement of poultry to free areas and confine birds to protect them from infection.
They should avoid hunting, purchase and processing of wild birds, poultry farmers who visit sites within 1.5km used as shelter by wild birds should keep disinfecting their hands.

They should prevent restocking of farms with birds from unreliable sources including live bird markets.
Farmers must practise quarantining of newly introduced birds before mixing them with the rest and restrict access of visitors to farms including avoiding sharing of poultry farm equipment.

For those trading in poultry, the solution is to quarantine all live bird markets in affected areas, regular disinfection of markets and avoid mixing different bird species in a market including confining sick birds in a cage.
There are vaccines for a number of poultry diseases in Uganda such as Newcastle and Gumboro. For avian influenza, a vaccine is being developed in most affected regions such as Asia. It has an efficacy rate of 60 per cent and it induces immunity between three to six months.

What previous incidences of avian flu show about this outbreak

Dr Halid Kirunda, who did a study on avian influenza, explains previous incidences. He says “in 2006 and 2007, [Maaif] carried out surveillance. One bird in Yumbe district was found with fragments of the virus but did not die. In 2007, seven birds in Namayingo and Bugiri had been exposed to the virus and a good number died and in 2010 there were traces of the virus outbreak on Bussi Island in Lake Victoria where two ducks died”.

What is avian flu?

Avian flu is one of the diseases causes by avian influenza (AI) virus, which is specifically caused by a subtype known as H5N1.
AI viruses may cause natural infection in various domestic and wild bird species throughout the world. They have particularly been reported to occur in poultry either in the highly or low pathogenic (disease causing) forms.
These viruses are classified into 18 (H1–H18) and nine (N1–N9) strains for a total of 146 possible AI virus combinations.
AI virus strains are further classified as low pathogenic avian influenza (LPAI) or highly pathogenic avian influenza (HPAI) based on specific criteria. Most AI viruses are usually associated with mild disease in poultry. In contrast, HPAI viruses can cause severe illness and high mortality in poultry. LPAI viruses have the potential to evolve into HPAI viruses and this has been documented in some poultry outbreaks.

The main reservoirs
The types H5 and H7, including H5N1 (avian flu), H7N7, and H7N3 have been associated with poultry and human infection, while these have ranged from mild (H7N3, H7N7) to severe and fatal disease (H7N7, H5N1) in poultry. H5 and H7 viruses have been associated with severe disease and cause high mortality rates of up to 100 per cent in chickens and turkeys.
AI viruses have been isolated from at least 105 wild bird species of 26 different families.
Among all species where influenza viruses have been isolated, waterfowl and shorebirds are regarded the main reservoirs of these viruses. The prevalence has been reported in waterfowl, domestic birds and pigs in several parts of Africa.
Uganda is a seasonal shelter of about 240,000 of the estimated 50 billion birds that make seasonal movements between the temperate zone and the tropics.
Due to the favourable climate and several fresh waterbodies, Uganda serves as a destination for migratory birds with many remaining around for several months.

Spreading the virus
Among 20 species globally been categorised as high risk, eight are regularly observed in Uganda. These include Tufted duck, long-tailed Cormorant, Great Cormorant, Northern Shoveler, Garganey, black-headed gull and Eurasian Wigeon.
Waterbirds can be a source of low pathogenic (disease causing) viruses for poultry, in which they can evolve into highly pathogenic strains. Spread of viruses to domestic species can be favoured by the large number of non-wetland dependant groups (“bridge species” such as cattle and egrets) that move between free-living waterfowl and human settlements and may interact with domestic birds.
The other factors that may facilitate spread are the many live bird markets scattered across the country.

by Dr Halid Kirunda,
the director, Mbarara Zonal Agricultural Research and Development Institute NARO