A review of methods for preventing the transmission of highly pathogenic avian influenza in birds in high risk areas of infection

Influenza virus causes a highly contagious disease in both humans and animals. Due to the major occurrence of infection in 2013 to 2018, all regions were affected by HPAI outbreaks in domestic birds. The most affected regions were Europe and Asia. The Asian lineage HPAI H5N1 virus continued to be reported from countries in Asia and Africa in both poultry and wild birds. The virus has become enzootic in Asia and Africa and continued to cause outbreaks in poultry and sporadic human infections.The HPAI H5N8 outbreaks continued to be reported from a few countries in Europe, Africa, Middle East, and Asia in poultry or wild birds, so far no reports of human infection have been reported.HPAI H5N6 viruses first emerged in China in 2013 and have been reported by several Asian countries. The Asian lineage H5N6 causes severe clinical signs in poultry and associated mortality, and it has also been associated with human infection, including a number of deaths. Currently a new variant strain of HPAI H5N6 emerged and these outbreaks are ongoing in Asia and Europe. The HPAI H5N6 has been reported for the first time in the port of Kyashahr in Iran, by migration of wild birds.Because of worldwide outbreaks, veterinary services in at risk countries have recommended increasing prevention efforts through biosecurity to minimize contact between wild birds and poultry and enhancing surveillance and preparedness.Influenza viruses can be destroyed with a variety oflipid soluble disinfectants such as detergents, formalin, the oxidizing agents, the dilute acids (hypochlorite sodium) and ammonium ions. Avian influenza quickly disappear by high temperature, high or low acidity, nonisotonic and dry environmental conditions. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low.Because of the stability of the virus in the environment and highly contagious nature, strict biosecurity measures and good hygiene are essential in protecting against disease outbreaks. Prevention techniques can be improved by keeping poultry away from migration areas of wild fowl;strict quarantine and minimizing movements on and off the farm; maintaining strict control over contacting flocks to vehicles, people and equipment; reporting any bird illnesses and deaths to the Veterinary Services;Enhancing surveillance; early detection and Strengthening hygiene;ensuring appropriate disposal of manure, litter and eradicating the dead poultry; burring or incinerating the depopulated poultryand productsincluding faeces; and a period of at least 21 days before restocking. Episodic transmission of AI viruses to humans occurs when there is close contact with infected birds or heavily contaminated environments. People who are working withpoultry have to wear protective clothing, including face masks, goggles, gloves and boots.There is no evidence to suggest that the consumption of poultry or eggs could transmit the AI virus to humans. As a precautionary measure, suspected animalsshould not be allowed to enter the human food and animal feed chain.The outbreaks of HPAI across Asia has led to considerable use of vaccination as part of control policies, either as an emergency measure or prophylactically for both HPAI and LPAI.In countries with developing poultry industries,the farms should be placed far away from each other and from migratory waterfowl routes. Vaccination is not sufficient withoutthe application of monitoring systems. It should be consideredthat these viruses could become endemic in vaccinated poultry populations and antigenic and genetic changes in the virus can be caused by Long-term circulation of the virus in a vaccinated population.Prophylactic vaccination for viruses of the H5 and H7 subtypes is a completely innovative concept, it should generate a level of protective immunity in the target population by reducing levels of viral shedding.On the basis of data generated in recent outbreaks and due to the maintenance of animal welfare, we review the available control methods for avian influenza infections in poultry and human.

کلیدواژه ها:

HPAI ، Avian influenza ، H5N1 ، Shedding ، H5N8 ، Vaccination ، H5N6