Malaria



Dave Rushworth


The last episode dealt, briefly, with mosquitoes that one is likely to find in this region. Focus here will be on the various types of malaria - among some other diseases - transmitted by mosquitoes. The name malaria derives from ?malaria? (bad air) - from the swamp gases in marshy areas with which mosquitoes and the disease were associated.

?The recorded history of malaria dates back to around 500 BC in Greece, where it may have been introduced by infected slaves and contributed to the breakdown of ancient Greek civilisation.

As early as 46 BC the symptoms and various forms of malaria had been described but only around 116 AD was it linked with swampy ground and transmission by mosquitoes.

?It was well known in medieval Europe where its debilitating effect, with the decadence of that time, may have been a contributory factor in the fall of Rome. The disease, then known as ?the ague?, is thought to have been carried from Rome to Britain, where it was common until the draining of the Fens and embankment of some rivers around 1859.

Distribution

At the present time the disease is pantropical, occurring in most countries within that region - excluding Australia but apparently including northern New Zealand. Through the use of effective but environmentally damaging pesticides, mosquitoes were being successfully limited.

Since the banning of these chemicals around 1970, the reported cases of malaria have again increased. Around 250 million people are affected annually with 90% of the cases reported from tropical Africa and the bulk of the rest from India and Brazil. In South Africa, malaria is only considered a threat in the lowveld areas from northern KZN and Swaziland, in the south, to the Limpopo valley in the north.

Carrier Mosquitoes

The only vectors for the transmission of the malaria parasites in our area are some female mosquitoes of the Anopheles gambiae complex and the Anopheles funestus complex - of which the Anopheles arabiensis is probably the most important.

As mentioned previously - these mosquitoes can be identified by the manner in which they sit with ?tail? up at 45 degrees to the surface. The harmless males can be identified by the feathery antennae. No other mosquitoes are known to transmit malaria.

Transmission

The female Anopheles, which also feeds from plants, requires a ?blood meal? before her eggs will develop. If she bites a person infected with malaria she will ingest malaria parasites.

When she bites the next person she first injects an? anti-coagulant through which she passes the parasite on to the next person. After a good meal she will normally sit on a nearby wall for a while before flying off to lay her eggs.

Types of Malaria

There are four types of Malaria - all of the genus Plasmodium. The dangerous, malignant form is Plasmodium falciparum which is responsible for the majority of deaths. The other three benign forms are Plasmodium vivax, Plasmoduim ovale and Plasmodium malariae which cause a debilitating disease sometimes recurring over many years.

One reason for the difference in severity in their effect can be attributed to the preference of the different parasites for red blood cells at different stages of maturation. P. malariae prefers mature blood cells. P. vivax and P. ovale invade the younger blood cells. P. falciparum is indiscriminate in its choice of red blood cells - hence the broad scope and severity of its attack.

Effect on Humans

P. vivax - is not common among African blood types but otherwise common in the rest of the world. It ?hides away? in the liver and spleen and causes frequent relapses if not properly treated. It can result in severe anaemia and rupture of the spleen. Can? remain in the system for a long time.

P. ovale - similar to P. vivax but more common in West Africa, it produces fever spikes about every 48 hours. Untreated, the infection can remain for up to three or more years with more lengthy periods between attacks. P. malariae - can persist in low concentrations in the blood.

As the parasite builds up it causes a fever cycle that spikes every 72 hours and lasts for up to 10 hours. It breaks through for periods of as little as three, but up to 50 years and appears to be able to lie dormant for long periods. P. falciparum - is the dangerous form of malaria which requires immediate treatment. Like the other forms it normally takes one or two weeks to develop.

Typical fever spikes every 48 hours becoming less obvious with maturation of parasites. It can rapidly become severe in non-immune persons and can cause death in a short time. Cerebral damage appears to be caused by clogging of the capillaries to the brain by masses of damaged blood cells.

AT THE FIRST SIGN OF FLU-LIKE SYMPTOMS A FEW DAYS AFTER VISITING A MALARIA AREA - SEEK IMMEDIATE MEDICAL ATTENTION. PLAY IT SAFE AND RATHER TREAT UNDIAGNOSED CASES FOR MALARIA, ESPECIALLY IF SYMPTOMS ARE ACCOMPANIED BY A FEVER.

Treatment

I am not going to enter the arena of treatment as this is a medical matter and should be referred to qualified medical personnel - except for the above advice. There have been unnecessary deaths due to wrong diagnosis. All malaria in this part of the world is ?Chloroquine Resistant? and requires specialised medication.

Quinine is still an effective and reliable drug to use but seek informed medical advice from qualified and experienced medical staff. I have had most types of malaria, many times, from an early age. It is unpleasant but easy to cure if treated early. The most prolonged was vivax, which did not respond to the usual drugs and had to be treated with Primaquine.

If you think you have malaria get it treated. It is a notifiable disease which can be transmitted to others while you are infected. There is little chance of contracting the disease if you take the normally advised precautions and there is no need to become paranoid about every mosquito you see. Very few of them will be Anopheles.

Immunity

People living in a malaria area for extended periods can build up a form of immunity to the type of malaria in their specific area. The immunity is not effective if one moves to another area and can be lost through extended periods of absence from that area. Immunity is also destroyed by taking anti-malarial prophylactics. Don?t rely on possible immunity as a method of prevention.

Some years ago in the north west of Hwange National Park there were a lot of workers from the BaTonga people of the Zambezi valley. As with many of the people who had grown up in malaria areas, I suspect they had developed what is called 'sickle-cell anaemia? - a blood cell immunity.

At that time there were migrant workers coming out of the Congo for jobs in our area. During one wet season many of us in the camp went down with a strange variety of ?malaria? which caused extreme pain and swelling to all body joints. A decree came from the ?top brass? for all personnel to be dosed with prophylactics. I strongly advised againstm dosing those people from the valley but lost my case.

They were all duly dosed and almost immediately they ALL went down with the strange type of malaria. There were several deaths among those dosed and an investigation took place. The strange disease was eventually diagnosed as ?Chikungunya? or ?break-bone-disease?, which had been introduced from central Africa and spread by the Aedes aegyptii mosquito.

It apparently does not affect children (unlike Plasmodium) but can be lethal to adults, as was the case with many. It took ages, and in some cases years, for full recovery from the aches and rheumatic type joints - but it was a lasting lesson on immunity.

NOTE :- This article is intended to assist a better understanding of malaria and should not be used as a guide for treatment or any other liable action. Professional advice should always be sought.

?Statistics and specifics used have been quoted from - African Insect Life - by S.H.Skaife, and from the ?Layman's Guide to Malaria?? - by Martine Maurel and updated by Dr Stephen Toovey and Dr Andrew Jamieson (Struik). Both publications are readily available in most book shops. I can highly recommend the latter to those with a wish to know more about malaria.



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