Animal infections a threat

Animal infections becoming a global health threat to humans

8/19/2016 laboratory

The number of emerging infectious diseases affecting people has more than tripled since the 1940s. Nearly 60 per cent of all human diseases and 75 per cent of all new, emerging, or re-emerging infectious diseases affecting humans are diseases transmitted from animals to humans which are called zoonotic. These diseases can be viral, bacterial, fungal or parasitic. They can be spread directly from the animal, or indirectly through the environment, or by vectors such as mosquitoes or ticks. Zoonotic diseases include Ebola, Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), rabies, yellow fever and the latest emerging pandemic threat, the Zika virus. The Zika virus has been dominating global health news and it was also a subject of discussion at an Infectious Diseases conference held recently at Aga Khan University Hospital, Nairobi. Until very recently, few people had heard of the Zika virus even though the virus had been discovered by researchers in 1940s. In 1947, scientists studying yellow fever put a rhesus monkey in a cage on a tree in Uganda's Zika Forest. The monkey came down with a fever, but the cause was not yellow fever: It was something the researchers had never come across before and they named it after the forest. A year later they realised that mosquitoes transmitted the virus and that it could also infect humans. Fast forward to 2015, and a large epidemic covering much of the western hemisphere has resulted in millions of infections. These infections are usually mild, but are devastating to unborn infants whose mothers are infected. The infection results in microcephaly (small head) and multiple other brain abnormalities in the affected and infected baby. This has resulted in an epidemic of microcephaly that was initially recognised in Brazil. The virus is spread primarily by the Aedes aegypti mosquito, which is widespread throughout the tropical and sub-tropical regions, so there are fears that it will spread far beyond the western hemisphere. Ebola was first discovered in 1976 near the Ebola River in what is now the Democratic Republic of the Congo. Researchers believe that the virus is animal-borne and that bats are the most likely reservoir host of Ebola virus. The Ebola outbreak in West Africa in 2014 became the deadliest occurrence of the disease since its discovery in 1976. The disease was endemic in the West African countries of Liberia, Guinea, Sierra Leone, and also infected people in Nigeria, the US and Mali when infected individuals carried the virus to those countries. By the end of the epidemic, at least 11,315 people had died. Rabies is an infectious viral disease that is almost always fatal following the onset of clinical signs. In most human cases in sub-Saharan Africa, the rabies virus is transmitted by domestic dogs. Between November 2002 and July 2003, an outbreak of SARS in southern China caused an eventual 8,096 cases with 774 deaths reported in 30 nations with the majority of cases in Hong Kong, according to the World Health Organization (WHO). Scientists have identified bats as the natural reservoir of SARS-like coronaviruses. Closer home, Kenya recently reported its first case of yellow fever in 25 years in a patient from Angola, where an outbreak is currently happening. This prompted the Health Ministry to issue a countrywide yellow fever alert in all counties, hospitals and points of entry, including airports, for thorough screening to identify and isolate other possible cases. Although no human cases have been acquired in Kenya in the last 25 years, it remains endemic in monkeys. The disease is also transmitted among monkeys, and the risk for human infection remains high, particularly in the Rift Valley. Approximately 35 African countries as well as certain areas of South America are regarded as being at risk for yellow fever. The disease can be severe, causing bleeding, jaundice (yellow eyes and skin) and maybe similar to severe Ebola or dengue cases. In addition to zika, dengue, and yellow fever, chikungunya is another virus carried by Aedes mosquitos and is making a comeback in Somalia and North-eastern Kenya. It was originally described in Tanzania and the name in a local language refers to the bent over posture that results from the severe muscle and bone pain that are part of the infection. The infection is also widespread in India and has spread to the south-eastern part of the US. Zoonotic diseases continue to be of significant concern for public health. Maintaining animal health, using insect repellents, practising good personal hygiene, wearing protective clothing and undertaking vaccination where appropriate minimises the risk of some animal-borne diseases affecting people and significantly reduces the impact of emerging infectious diseases. By Professor Rodney Adam, Chair, Infection Control, Microbiologist and Infectious Diseases Specialist at Aga Khan University Hospital

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Animal infections becoming a global health threat to humans

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