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February 22, 2019

Malaria: Mosquitoes are not the only bad guys

NOT GUILTY? A mosquito is bloated with blood as it inserts its stinger into human flesh
NOT GUILTY? A mosquito is bloated with blood as it inserts its stinger into human flesh

As the rains begin, a relief for most, mosquitoes will return in numbers.

‘Mosquito’ means ‘little fly’ and there are over 3,500 species, which feed on the blood of various animals including mammals, birds, reptiles and even fish.

A mosquito flies more than two kilometres in search of food, can detect carbon dioxide from human breath at a few hundred metres and smell human skin at 50 metres.

Typically, it is the female mosquito that bites, as she needs blood protein in order to lay eggs; but she does not live on blood alone, spending time to take in nectar into a separate stomach, which gives her sugar.

Given time and space, a mosquito will bite and fill her stomach with up to 0.1 millitres of blood, 500 bites is the equivalent of a teaspoon of blood. Trying to get blood is a high risk yet necessary activity and female mosquitoes are very persistent.

Interrupt her blood meal and she will seek another victim sucking until the belly is full because at the end of the day she has to lay about 250 eggs.

She then rests two to three days and is back on the prowl looking for another victim. Like most insects, the mosquito goes through four stages of development, from egg, larva, pupa and then adult. The first three stages occur mainly in water, so the mosquito needs some stagnant water somewhere to lay her eggs. The clever thing is that even where there is drought, development can pause until the rains come before hatching.

It is therefore interesting how individuals deal with mosquitoes. There are those with time and a supreme sense of control of their own destiny who attack each mosquito, either slapping them to death on the wall or between their palms; gleefully happy at their sense of achievement, unaware that perhaps two days earlier that mosquito had set the scene for 250 more to attack.

Then there are those who spray everything in sight including their own food with insecticide. A third group follow ministry of health guidelines and sleep under an insecticide treated bednet. What is missing in all these measures is the strategy on what to do about the 250 mosquitoes that are growing elsewhere ready to attack as they mature.

A strategy to reduce these malaria-infested mosquitoes requires a review of the environment that you live in and knowledge of where your neighbour’s traveling patterns. Around your home, outside the house, there are often little containers, patches of ground that form puddles in the rain, ideal homes for a growing mosquito family. Then there are your neighbours, those living within two kilometres or so.

The major source of malaria, other than mosquitoes, are human beings. A mosquito will bite one person, then the next transmitting the mosquito parasite in the process. Studies show that persons travelling from malaria endemic zones mainly from western Kenya import infections to low malaria zones like Nairobi.

That means no matter how much clapping of mosquitoes, spraying you do; as long as your neighbours are not as dedicated in trying to manage the environment, much of your investment is wasted as you remain at risk of contracting malaria.

The solution to reducing the risk and burden of malaria is thereforeto have a community approach incorporating multiple ways of attacking the disease.

At the individual level sleeping under an insecticide treated bednet especially for children and pregnant women is very important. At a family level, making sure that around the house there are no sites for mosquitoes to breed adds a further level of protection. The use of and indiscriminate disposal of plastic containers means that this has to be a regular activity. At a public health level greater awareness of the risk and potential spread of the disease by people who travel a weekend to a malaria zone are bitten, return to the city and infect the poor mosquito needs to highlighted.

When upcountry, sleep under a net as well and do the same things toreduce the number of mosquitoes.

In malaria endemic areas, countyhealth officials are meant to conduct indoor residual spraying using long lasting insecticides. Having drainage that works rather than pools water is an effective strategy against malaria. Finally if symptoms of malaria do appear prompt treatment prevents further spread, while treating the individual concerned.

In a way malaria control is much like trying to fight corruption it requires the entire community to decide that it will no longer tolerate the disease. We could leave it to a specialized agency, expecting them to report back one day that they have done it and malaria is no more. The problem is that malaria is a disease of humans transmitted by mosquitoes. That means it is human beings who need to change their behaviour to reduce the malaria burden.

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