Malaria

The French carried about 8 million stays in the tropics each year, many opportunities to be exposed to malaria. In this context, the role of Field Operations is twofold: to correctly advise consultants to reduce as far as possible, the risk of malaria during or subsequent to a journey in endemic areas, but also know very diagnose quickly a malaria patient’s return in order to avoid serious complications or even death of the patient (a score of deaths each year in France). The aim of this chapter is to expose this process, after reviewing a few notions of Parasitology necessary for the proper understanding of prophylactic and therapeutic recommendations.

UNDERSTANDING THE PARASITE CYCLE:

Malaria (called malaria in many countries) is a disease resulting from infection by a parasite of the genusPlasmodium, of which there are four species: falciparum, vivax, ovale and malariae. These are intracellular protozoa. The disease occurs throughout the tropical regions of the world, and an estimated 3 million deaths resulting from infection each year. The female Anopheles mosquitoes transmit the disease to humans during a blood meal.

These mosquitoes have previously collected Plasmodium gametocytes in another patient man. The sexual phase of reproduction of Plasmodium takes place in the body of Anopheles. This phase result from new parasitic forms called sporozoites, which mosquitoes transmit (Fig. 1). In humans, the sporozoites earn the liver to undergo a new phase of maturation and proliferation in hepatocytes. This phase takes place during the incubation period is completely asymptomatic. It takes about ten days for P. falciparum, but sometimes several months for other Plasmodium species. Once completed hepatic phase of the cycle, the parasites are released into the bloodstream in the form of merozoites, earning the erythrocytes where they transform into trophozoites, visible to the examination of blood smears. Thus began the erythrocyte phase, that of the disease. Trophozoites will multiply within red blood cells that eventually rupture, releasing new merozoites that maintain the erythrocyte phase and therefore the disease. Antimalarial available today affect erythrocyte phase of the parasite cycle. They thus eliminate the parasitic forms responsible for the clinical manifestations, but not those of the previous stages of the parasitic cycle.

Sometimes the parasite “pause” to liver stage (P. vivax and P. ovale), or erythrocyte (P. malariae). The cycle will take several months or even several years after the infective bite, explaining the revival of access that can be observed with these three Plasmodium species.

PROTECTION AGAINST MOSQUITO BITES AND MALARIA CHEMOPROPHYLAXIS:

We must convince travelers of the importance of the observance of these safeguards that go together. Nearly 75% of cases of imported malaria are diagnosed in people from Africa who reside in France and who have become infected during a trip to their country of origin. Particular attention must be paid to preparing the trip for these subjects, especially if they travel with young children. They are particularly vulnerable to serious complications of the disease, as are pregnant women (see Box 3).

Protect the traveler against mosquito bites:

Anopheles mosquitoes bite between sunset and sunrise, it must act at the end of the day and born overnight. The barriers are mechanical and chemical, which are summarized in Box 1.

Box 1. Ways to protect yourself against mosquito bites
Habitat
Protect openings parts by fences
Use insecticides at night in the rooms
Sleeping under a mosquito net:
– In good condition, without holes
– Impregnated with pyrethroids *
– Correctly installed, that is to say to the floor or lining the mattress
Traveler
Avoid going out in the evening if possible
Evening wear long and loose clothing impregnated with pyrethroids *
** Use repellents to be applied on all exposed parts of the body, including face (watch the eyes and mouth, no spray to the face!). They should only be applied on healthy skin.
The term of protection varies from 2 to 12 hours, varying depending on the composition and concentration of the product used, climatic conditions, sweating, baths and showers
Warning: for children and pregnant women, we must carefully follow the manufacturer’s recommendations for use. Some repellents are cons-indicated in young children.
Notes
* Pyrethroid impregnation kits (deltamethrin or permethrin) for clothes and mosquito nets are available in pharmacies or in specialized stores. They are resistant to washing and have a persistence of several weeks or months (see user guide, variable depending on the product).
** DEET (diethyl toluamide) and KBR 3023 (1-methylpropylester or Icaridin) are products that have demonstrated the greatest effi ciency. We must be attentive to the composition of the prescribed product, as the active ingredient and its concentration varies from one specialty to another, and for the same specialty, a presentation to the other (lotion, spray, stick, cream , adult or child form).

Prescribe chemoprophylaxis:

Chemoprophylaxis is essentially justified to prevent malaria P. falciparum solely responsible for cerebral malaria that kills. This is unfortunately also P. falciparum which has a common resistance to chloroquine, forcing the use of other antimalarial more expensive and often less well tolerated. Chemoprophylaxis does not prevent infection and has no effect on the pre-erythrocytic forms of the parasite cycle. It simply abort the erythrocyte stage manager noted clinical manifestations. Chemoprophylaxis should be maintained until the cycle is complete liver.

Given that over 90% of cases of imported malaria P. falciparum incubation time is less than a month, it is recommended that chemoprophylaxis one month after the return (except for Malarone® which is effective on hepatic forms of P. falciparum and may therefore be taken only during 7 days after the transmission box output).

Rare cases of malaria due to P. falciparum may occur in subjects having properly performed chemoprophylaxis, either because of the antimalarial resistance used, or an unusually long incubation period of several months. In the latter case, the erythrocyte cycle occur as chemoprophylaxis, interrupted as expected a month after the release of the exhibition area allows not prevent the onset of clinical signs.

Antimalarial available for malaria chemoprophylaxis in 2008 are shown in Box 2.

Box 2. Antimalarial available for chemoprophylaxis
Chloroquine: Nivaquine®
Chloroquine + proguanil: Nivaquine® + Paludrine®, Savarine®
Proguanil + atovaquone: Malarone®
MEFL oquine: Lariam®
Doxycycline: many generic

The prescription of chemoprophylaxis will be personalized and choice of malaria molecule will depend on several criteria, including the indicative list is given in Table I. For travel less than 8 days to areas of low transmission, it can be assumed not to prescribe chemoprophylaxis, provided that the traveler effectively protects against mosquitoes, always near a medical center and adapted to know in an emergency in case of fever during the stay and within two months after the return.

The list of countries included in the special issue “Health health travelers and recommendations” of the Weekly Epidemiological Bulletin 1, regularly updated. We also find in this document the recommendations on the choice of malaria by country of destination. These recommendations are updated regularly based on constantly updated epidemiological data. The countries visited are classified as Group 1, 2 or 3, depending on the frequency of resistance to chloroquine and proguanil. It is important to always refer to the text of the latest recommendations, as significant changes occur each year. Antimalarial prescribing the manner in which group the country of destination are shown in Table II. The prescription of a reserve treatment, take without medical advice during the stay, mainly designed for travelers to very remote areas, or more rarely for travelers making repeated visits and brief transmission area.

Self-treatment will be taken in case of fever occurs over a week after the entry into transmission area and only in the absence of medical care available in twelve hours. It is necessary that the traveler has understood that even if the treatment is taken, it should consult a medical team as quickly as possible. It is also useful to remember that the prescription of a treatment is not subject to exemption from the application of protective measures against mosquito bites or chemoprophylaxis, it will resume after self-treatment. The choice of treatment provided will consider the prescribed malaria chemoprophylaxis for advance. The molecules used are oral quinine, mefloquine, atovaquone and proguanil +. In practice, the subject of treatment must remain an exception of prescription, highly supervised, explained at length the traveler before departure and performed by a physician trained in the use of antimalarials.

Box 3. Prophylaxis: what to remember
A population at particular risk of infection: African subjects from residing in France and traveling back to their countries of origin.
People particularly at risk for serious complications: children and pregnant women.
No bite, no malaria! Protection against mosquito bites is not incidental!
Prescribe appropriate chemoprophylaxis (destination, age, side effects and against-indications, pregnancy, cost).
Chemoprophylaxis recommendations should be updated regularly, we must remain vigilant.
There is no total protection: malaria is possible even in patients with well observed protective orders.
Educate the traveler to consult urgently before any febrile disease occurring over a week after the entry into area of ​​malaria transmission, and up to three months after leaving the risk area. And do not forget to do the same with children who have also traveled, the urgency is even greater for them!

OBJECTIVE OF THE CONSULTATION AFTER TRIP: DIAGNOSTIC RAPID ACCESS PALUSTRE:

The main problem for the practitioner is to find out as quickly diagnose a malaria attack, essential to avoid complications or death. Diagnosis is always simple … from the moment it evokes! The purpose of this chapter is not to describe in detail the malaria and its complications, but to emphasize the clinical context that needs to alert and remind misleading forms that can take the disease. Diagnosis is based on clinical and biological data.

Clinical and biological context:

Above all, a recent trip to malaria transmission area must be systematically sought during the interrogation of any consultant for a febrile patient pathology.

This is the prerequisite. Then the rule is simple: if the patient has been exposed, malaria diagnosis should be considered (Box 4). Most often, the malaria attack is manifested by fever, digestive disorders with nausea and epigastric pain (table of “febrile upset stomach”), and headache that rarely fail.

However, beware, the diagnosis should be considered “although”

– Even if the patient correctly followed its chemoprophylaxis and is well protected against mosquito bites;

– Even if there are clinical signs of orientation: Malaria may be accompanied by cough, vomiting and / or diarrhea, or abdominal pain. The danger is then too quickly diagnose bronchitis or gastroenteritis for example, by losing precious hours;

– Even if one is in full flu epidemic, and the patient has symptoms of an ordinary flu!

– Even if the fever is not paced (it usually is not the beginning);

– Even if the clinical condition is no immediate concern.

The pediatric formulations can be even more misleading with such a fickle fever. The level of suspicion should be high before the infant or small child who stayed in the area of ​​transmission and consultant for specific symptoms (vomiting, diarrhea, cough, anorexia …), even without fever. In this context, the search for malaria should be undertaken without delay.

In addition to clinical signs, additional tests often show biological disturbances that enhance diagnostic suspicion: thrombocytopenia, increased transaminases, leukopenia. Hyperbasophilic lymphocytes may be present, and it should not be so slow to find mononucleosis as part of a viral infection.

Biological diagnosis of malaria:

It is to highlight the presence in the blood of the parasite. For this, no need to wait for the next thrill or the next febrile peak! The plasmodium research needs to be done immediately, and the result must be made the same day, within two hours after collection. The technique remains the first-line blood smear, feasible in any laboratory, and allowing the calculation of the parasitemia and the diagnosis of Plasmodium species.

The thick blood, technically more demanding and longer to realize, is more sensitive hand. It is not done in the context of the emergency. Other diagnostic tools are sold today mainly used by laboratories for Parasitology: Research HRP antigen 2 or parasitic LDH. Their sensitivity or specificity is not greater than the reference method (smear and thick drop), but these tests have the advantage of technical simplicity, speed and the ability to establish a retrospective diagnosis.

A negative research does not rule out the diagnosis of malaria. If the clinical and biological context remains evocative, you have to repeat the exams.

Box 4. Diagnosis of Malaria: what to remember
Malaria is diagnosed interrogation, based on research from a trip to exhibition area during the past months.
Any fever occurring after a stay in malaria transmission area must be considered a malaria until proven otherwise, even if the clinical picture moving towards another diagnosis.
In infants and small children, the presentation can be very misleading, fever may miss. It is the notion of stay in transmission area that can suggest the diagnosis.
There are late forms of falciparum malaria, over two months after the release of the transmission area.
Once the referred diagnosis, research plasmodium must be carried out immediately, and the result must be returned the same day.
A negative research does not rule out the diagnosis: you have to know repeat the search if symptoms persist and remain evocative.