Mosquito-transmitted Zika virus may spread to Nigeria
• Disease comes with second-hand tyres from S’Asia
ZIKA virus, a mosquito-borne disease that has swept quickly throughout equatorial countries, may spread across the Americas, the United States and even Nigeria, the World Health Organisation (WHO) has warned.
According to a WHO fact sheet, Zika virus infection, which is caused by the bite of an infected Aedes mosquito, usually causing mild fever, rash, conjunctivitis, muscle pain and headache, has already been found in 21 countries in the Caribbean, North and South America.
The virus has also been linked to thousands of babies being born with underdeveloped brains following which some countries have advised women not to get pregnant.
The Guardian’s investigation reveals that Nigeria, which is one of the malaria-endemic countries, is home to the Aedes aegypti, also a vector for malaria, yellow fever and dengue fever.
It has also emerged that Nigeria is in danger of dengue fever outbreak, another deadly fever in the class of Ebola Virus Disease, transmitted by Aedes aegypti mosquito (yellow fever mosquitoes) and Aedes albopictusis (tiger mosquitoes) that are now common in the country mostly in and around homes.
The WHO defines a public health emergency of international concern as “an extraordinary event which is determined to constitute a public health risk to other states through the international spread of disease and to potentially require a coordinated international response.”
A virologist and Director of WHO National Polio Laboratory, Department of Virology, University of Ibadan (UI), Oyo State, Dr. Adekunle Adeniji, had in 2014, warned: “There is no house that these mosquitoes are not present, including big hotels. We have all the four stereotypes of dengue fever in Nigeria. Although not all mosquitoes are infected with dengue virus, if bitten by an infected one, it will spread the virus.”
The expert said the mosquitoes, black and tiny, with white patches, look alike, adding that in a recent case people thought was Ebola virus disease turned out be a case of dengue fever.
He said dengue virus had been isolated by the Department of Virology as far back as the 70s from humans and mosquitoes, declaring that Aedes albopictusis was not native to Africa, but found its way into Nigeria through the international trade in used tyres, where their eggs were deposited.
Although there is yet no outbreak of Zika virus and dengue fever in Nigeria, the expert urged Nigerians to protect themselves from being bitten by mosquitoes and to maintain clean environment.
According to a study published in New York Science Journal, dengue viruses (serotypes 1-4), are the causative agents of dengue fever, dengue haemorrhagic fever and dengue shock syndrome in humans and are transmitted predominantly by the Aedes mosquitoes.
Arbovirus infections are usually sensitive to changes in rainfall and temperature. Consequently, their transmission intensity may be regulated by weather and climate.
The study titled “The Effect of Climate on Dengue Virus Infections in Nigeria,” was conducted by M.M. Baba and Muhammad Talle from the WHO National Polio Laboratory University of Maiduguri Teaching Hospital, Borno State.
According to a study by researchers from the Department of Biological Sciences, University of Agriculture, Abeokuta, Ogun State, Aedes aegypti bred in all the breeding sites including tree holes. This indiscriminate breeding habit has long been reported by Okorie (1970).
The high occurrence of Aedes albopictus in discarded tyres could probably be due to its adaptable life to this habitat.
The study was published in Tanzania Journal of Health Research and titled: “Mosquito larval habitats and public health implications in Abeokuta, Ogun State, Nigeria.”
According to the study: “The widely spread occurrence of Aedes albopictus in Nigeria has been receiving attention since early 1990s when its presence was first observed in some rural areas in Delta State.
Aedes albopictus is a native of South-Asian countries where it has been known as an efficient vector of yellow fever and dengue.
“The vector was imported to Nigeria through second-hand tyres.
As a result, the preponderance of Aedes albopictus is being speculated to be occurring in cities where tyre business booms or where improper management of used tyres is being practised. During this study, tyres were seen in many residential areas with no specific function, and in few cases, they were either used for erosion control or plant guard.
Both Aedes aegypti and Aedes albopictus have been implicated in the transmission of yellow fever and other arboviruses,” the study noted.
Meanwhile, a May 2015 outbreak of Zika in Brazil led to nearly 3,500 reports of birth defects linked to the virus, even after its symptoms had passed, and an increase in cases of Guillain-Barre syndrome, an immune disorder.
The United States Centre for Disease Control and Prevention (CDC) has issued a travel alert advising pregnant women to avoid countries where the disease has been recorded.
The virus was isolated for the first time in 1947 in the Zika forest in Uganda. Since then, it has remained mainly in Africa, with small and sporadic outbreaks in Asia. In 2007, a major epidemic was reported on the island of Yap (Micronesia), where nearly 75 per cent of the population was infected.
On March 3, 2014, Chile notified the Pan American Health Organisation (PAHO)/WHO that it had confirmed a case of indigenous transmission of Zika virus on Easter Island, where the virus continued to be detected until June 2014.
In May 2015, the public health authorities of Brazil confirmed the transmission of Zika virus in the northeast of the country.
Since October 2015, other countries and territories of the Americas have reported the presence of the virus.