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Concerns over mosquito-borne diseases

By Chukwuma Muanya
19 September 2019   |   3:51 am
There are fresh concerns over global spread of mosquito-borne diseases as a species, Aedes aegypti, that can carry Zika virus, dengue and yellow fever has been discovered in Nebraska, United States (U.S.), for the first time.


*Scientists discover species that carry zika virus, dengue, yellow fever
*Why Nigeria is still missing as malaria vaccine inaugurated in Kenya

There are fresh concerns over global spread of mosquito-borne diseases as a species, Aedes aegypti, that can carry Zika virus, dengue and yellow fever has been discovered in Nebraska, United States (U.S.), for the first time. Aedes aegypti, the yellow fever mosquito, can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognised by white markings on its legs and another in the form of a lyre on the upper surface of its thorax.

According to a study published in New York Science Journal and titled “Diversity and distribution of Aedes mosquitoes in Nigeria”, Aedes mosquitoes are abundant and widely distributed across Nigeria. The researchers from the National Arbovirus and Vectors Research Centre (NAVRC), Enugu, collected a total of 8,659 Aedes mosquitoes, consisting of nine different species. Aedes albopictus 3,651 (42 per cent) constituted majority of the collections, while Aedes circumluteolus 40 (0.5 per cent) was the least collected. All nine species collected in the surveillance were present in Enugu State, while Kaduna State, with the least diversity, had only one species.

The researchers concluded: “The study revealed the overwhelming presence of domestic, peri domestic and canopy breeders of the genus, Aedes, in the country. These include those that transmit some of the most dreaded diseases across the globe. Hence, there is need to continuously update available data on these mosquitoes. This should be the basis for effective vector control and the eventual elimination of Aedes-related diseases in Nigeria.”

Meanwhile, the Nebraska Department of Health and Human Services (DHHS) said that it found Aedes aegypti mosquitoes in York County – about 100 miles from the capital of Omaha – on Tuesday. State and local officials captured the mosquitoes during a yearly effort to track the number of pests carrying West Nile virus in Nebraska, according to a statement.

Despite the fear of tropical diseases spreading throughout the state, health officials say that the risk of transmission is very low.A. aegypti originated in Africa, but has since become one of the most widespread mosquito species in the world.

Meanwhile, despite having the highest burden of malaria in the world, Nigeria is still missing as Kenya joins Ghana and Malawi to launch the world’s first vaccine for the mosquito-borne disease.The World Health Organisation (WHO) has congratulated the Government of Kenya for launching the world’s first malaria vaccine on Friday, September 13, in Homa Bay County, western Kenya.

The malaria vaccine pilot programme is now fully underway in Africa, as Kenya joins Ghana and Malawi to introduce the landmark vaccine as a tool against a disease that continues to affect millions of children in Africa.The vaccine, known as RTS,S, will be available to children from six months of age in selected areas of the country in a phased pilot introduction. It is the first and only vaccine to significantly reduce malaria in children, including life-threatening malaria.

According to the Nebraska DHHS, A. aegypti mosquito bites primarily in the daytime and only feeds on people. State epidemiologist for the DHHS, Dr. Tom Safranek, told that health officials were surprised when they found an A. aegypti mosquito in traps meant for West Nile-mosquitoes.
“It was almost like they didn’t believe their eyes,” he said. “We put out traps to trap A. aegypti and, what do you know, we found between 40 and 50.” The mosquitoes have not been tested yet to see if they carry the viruses that cause those diseases.

However, Safranek said that for a mosquito to transmit the diseases, it would need to bite an infected person, and then bite an uninfected person. Additionally A. aegypti can only fly about 500 feet. “We think the transmission risk is low,” he said. “But we have a scenario where it could occur, and we haven’t had that before. So there’s a possibility.”

The mosquitoes will undergo genetic testing to pinpoint where they came from and then will undergo testing for the viruses.One theory of how the mosquitoes arrive in Nebraska is in eggs from another state – but this has not been proven yet. “They can get moved around like transpiration of materials like tires, anyplace where the eggs can get moved,” said Safranek. In Nebraska, only one case of dengue fever and one case of Zika virus has been reported this year, according to the Centers for Disease Control and Prevention.

In both instances, the patients traveled to areas where the viruses are common, and were not infected locally. Health officials recommend that resident protect himself or herself by wearing long sleeves and pants as well as bug spray when going outside.They also suggest draining any standing water from places such as bird baths and buckets because mosquitoes are attracted to still water. The Nebraska DHHS did not immediately return’s request for comment.

According to the WHO, malaria remains one of the world’s leading killers, claiming the life of one child every two minutes. Most of these deaths are in Africa, where more than 250,000 children die from the disease every year. Children under-five are at greatest risk of its life-threatening complications. Worldwide, malaria kills 435,000 people a year, most of them children.

In Nigeria, it is estimated that Nigeria loses N132 billion yearly and records estimated 100 million cases with over 300,000 deaths yearly to malaria and its complications.Why was Nigeria not chosen for the vaccine trial? The WHO explained: “Following a request by WHO for expressions of interest, the pilot countries were selected from among ten African countries. Key criteria for selection included well-functioning malaria and immunization programmes, and areas with moderate to high malaria transmission.”

What informed the pilot studies? Proven results: Thirty years in the making, RTS,S is the first, and to date the only, vaccine that has demonstrated it can significantly reduce malaria in children. WHO Regional Director for Africa, Dr. Matshidiso Moeti, said: “Africa has witnessed a recent surge in the number of malaria cases and deaths. This threatens the gains in the fight against malaria made in the past two decades.

“The ongoing pilots will provide the key information and data to inform a WHO policy on the broader use of the vaccine in sub-Saharan Africa. If introduced widely, the vaccine has the potential to save tens of thousands of lives.”Distinguished health officials, community leaders and health advocates gathered in Homa Bay County – one of eight counties in Kenya where the vaccine will be introduced in selected areas – to mark this historic moment with declarations of support for the promising new malaria prevention tool and to demonstrate a ceremonial first vaccination of a six-month-old child.

Speaking at the event, WHO Representative to Kenya, Dr. Rudi Eggers said: “Vaccines are powerful tools that effectively reach and better protect the health of children who may not have immediate access to the doctors, nurses and health facilities they need to save them when severe illness comes. This is a day to celebrate as we begin to learn more about what this vaccine can do to change the trajectory of malaria though childhood vaccination.”

Thirty years in the making, the vaccine is a complementary malaria control tool – to be added to the core package of WHO-recommended measures for malaria prevention, including the routine use of insecticide-treated bed nets, indoor spraying with insecticides and timely access to malaria testing and treatment.

The Ministry of Health, through the National Vaccines and Immunization Programme, is leading the phased vaccine introduction in areas of high malaria transmission, where the vaccine can have the greatest impact.The aim is to vaccinate about 120 000 children per year in Kenya across the selected introduction areas, including Homa Bay, Kisumu, Migori, Siaya, Busia, Bungoma, Vihiga and Kakamega counties. Within the eight counties, some sub-counties will introduce the vaccine into immunization schedules while others are expected to introduce the vaccine later.

The WHO-coordinated pilot programme is a collaboration with the ministries of health in Ghana, Kenya and Malawi and a range of in-country and international partners, including PATH, a non-profit organization, and GSK, the vaccine developer and manufacturer, which is donating up to 10 million vaccine doses for this pilot.

Financing for the pilot programme has been mobilized through an unprecedented collaboration among three key global health funding bodies: Gavi, the Vaccine Alliance; the Global Fund to Fight AIDS, Tuberculosis and Malaria; and Unitaid.

Proven results: Phase 3 clinical trials were conducted between 2009 and 2014 through a network of African research sites, including three sites in Kenya (Kombewa, Siaya and Kilifi) involving more than 4,000 Kenyan children. Children receiving four doses of RTS,S experienced significant reductions in malaria and malaria-related complications in comparison to those who did not receive RTS,S. Health benefits of the vaccine were in addition to those already seen through the use of insecticide-treated bed nets; prompt diagnosis; and effective antimalarial treatment.

Child vaccination schedule in Kenya: The vaccine, where available, will be given in four doses: three doses between six months and nine months of age, and the fourth dose at 24 months (age two).

Pilot countries: Kenya is one of three countries selected from among 10 African countries for the phased introduction of RTS,S following a request by WHO for expressions of interest. Key criteria for selection included well-functioning malaria and immunisation programmes and areas with moderate to high malaria transmission.