25.     Malaria & pregnancy.

Introduction.

Malaria remains a huge killer, responsible for between 1 and 3 million deaths each year.

Mostly of children under 5 years in sub-Saharan Africa.

This puts it in the same league as HIV and the one we tend to forget TB.

List of contents.

  1. introduction

  2. key facts for the DRCOG

  3. expanded information for the MRCOG

  4. background reading

  5. possible essay questions

  6. facts about malaria

  7. malaria and the UK

Key facts for the DRCOG.

  1. there are ~ 2,000 cases of imported malaria per annum in the UK.
  2. it is caused by infection with the Plasmodium protozoan.
  3. transmission is via the bite of the female Anopheles mosquito.
  4. about 70% are due to the potentially lethal Plasmodium falciparum.
  5. most cases are due to no prophylaxis or inappropriate prophylaxis.
  6. pregnancy reduces resistance to malaria.
  7. a woman born and raised in an endemic area develops some immunity to infection, but this diminishes once she lives out of the endemic area.
  8. HbS, HbC and glucose-6-phosphate dehydrogenase deficiency provide some protection against infection.
  9. non-immune women should be advised to keep away from endemic areas when pregnant.
  10. immune women who leave and then return to an endemic area should be informed of their increased risk of infection from the effect of pregnancy itself and the reduction in their natural immunity.
  11. incubation period is 7 10 days for P. falciparum; longer for the other types.
  12. P. falciparum infection is the biggest risk in pregnancy.
  13. clinical features include: fever, rigors, severe headache, vomiting, anaemia, jaundice, hepato-splenomegaly and abdominal and muscle pain.
  14. P. falciparum malaria in pregnancy is associated with maternal risk: death, cerebral malaria, hyperpyrexia, severe anaemia, hypoglycaemia, renal failure and pulmonary oedema.
  15. its not good for the pregnancy either: increased IUGR, prematurity and stillbirth rates and a probable increase in the risk of miscarriage.
  16. congenital malaria occurs but is rarely serious due to transfer of maternal antibodies.
  17. basic measures to prevent being bitten remain important: window screens, closed doors etc. that keep the little buggers out, especially at night when they are most active, clothing covering exposed parts, bed nets, insect repellents, insecticide vaporisers, coils etc.
  18. drugs for prophylaxis and treatment need to be determined by the type of infection prevalent in the area being visited, the degree and nature of drug-resistance etc.

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Expanded information for the MRCOG and to make facts stick.

Background reading.

There is a very good TOG article by Gitau and Eldred (2005; 7:5-11).

MRCOG candidates should read this and create cards.

There is also a good summary in "Nelson-Piercy".

These two sources provide all you need for the exam.

This topic had not featured in the MRCOG essays at the time of writing (February 09).

So the TOG article makes it a likely candidate for an appearance in the near future.

There are lots of internet sites with additional information if you want it.

E.g. the Centers for Disease Control and Prevention.

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Possible essay questions.

An essay could be:

        a generic essay about malaria in relation to pregnancy,

        or a more specific one about the patient who comes to see you as:

                she plans to visit an endemic area for a year,

                to accompany her husband who will be working there,

        or a patient who is off-colour and febrile on her return from a malarial area.

With the second essay, you would need to think about air travel too.

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Facts about malaria.

Malaria is getting worse as:

            the vector, the vector, the Anopheles mosquito, is becoming resistant to more insecticides,

            and the Plasmodium bug is developing greater drug-resistance.

WHO figures are that it causes up to 3 million deaths each year.

The majority are in young children in sub-Saharan Africa.

Presumably if you get beyond the early years you develop some immunity.

You will remember from undergraduate days that it is caused by infection with the protozoan parasite, Plasmodium.

There are 4 species: P. falciparum, P. malariae, P. vivax and P. ovale.

The relationship between this protozoan and malaria was first noted by Alphonse Laveran in 1880.

He was awarded a Nobel Prize in 1907 for this and related work, but only after a long battle against sceptics.

How often does this story recur in the history of medicine?

There is a nice account on the CDC website: CDC website.

This includes a copy of a drawing made by Laveran to depict what he had found.

P. falciparum is the most common cause of infection and by far the nastiest.

It is almost always the parasite associated with a malaria death and is the cause of cerebral malaria.

Ovale and vivax can lie dormant for ages then flare up to cause a relapse.

My beloved old grandfather, Jo Patten, worked on the railways in Nigeria for most of his working life.

Inevitably he contracted malaria and used to get occasional relapses for decades after he retired.

He would dose himself with quinine and whiskey, retire to bed for a day or two and return hale and hearty.

The parasite can be injected by the bite of the female Anopheles mosquito.

Like vampires:

        they mainly come out at night to feed,

        so this is the time that it is especially important to take precautions to avoid being bitten.

It can also be transmitted:

        via blood transfusion,

        and from mother-baby, though rarely.

The injected form of the parasite is called a sporozoite.

It hastens to the liver where it develops for about a week, turning into 20,000 merozoites.

Imagine if we reproduced on the same scale you would be a nation in a matter of weeks!

The merozoities leave the liver:

        and invade red blood cells,

        where they continue to develop before destroying the red cells they inhabit,

        and going on to infect other red cells.

This produces the main effects: cerebral malaria and severe anaemia.

Cerebral malaria is defined as:

        severe coma with evidence of falciparum infection,

        but no other cause of the coma.

In clinical practice, it is widened to include:

        all patients with neurological features,

        evidence of falciparum infection,

        and no other explanation for the neurological features.

What causes it?

Apparently this is not clear and there are various contributory factors.

The infected red cells clog the small vessels in the brain causing hypoxia.

Hyperpyrexia is a common feature and can produce loss of consciousness, convulsions etc.

Some of the drugs, e.g. chloroquine can cause convulsions and psychiatric symptoms.

Malaria itself causes hypoglycaemia as do some of the associated drugs.

A common symptom is severe vomiting leading to electrolyte abnormalities, especially hyponatraemia.

Severe anaemia can occur and manifest itself with cerebral symptoms.

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Malaria and the UK.

The Health Protection Agency (HPA) collects data about malaria in the UK.

There were 1758 cases in 2006 and 1548 cases in 2007.

There has been a gradual decline since the mid-90s when the numbers were ~ 2,500.

About 70% of cases are due to plasmodium falciparum.

There were 5 deaths in 2007, 4 contracted the disease in Africa, 1 in India.

Sub-Saharan Africa is the biggest source of the infections: 1006 of the total of 1548 in 2007.

By comparison, there were 199 cases from Asia.

The HPA found that:

        83% of those who became infected had not taken prophylaxis,

        and that most of the rest had not taken appropriate prophylaxis for the area they were visiting.

This accentuates one of the basic facts:

        malaria varies widely geographically in type and drug-resistance,

        so both prophylaxis and treatment need to be tailored to the area.

 

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