Malaria
From WikiLectures
| Plasmodium spp. | |
| Haematozoa | |
| Plasmodiidae | |
| Plasmodium ovale, trophozoite | |
| Occurrence | tropical belt |
|---|---|
| Disease | malaria, various forms |
| Infectious stage and method of infection | sporozoite - inoculative (for mosquito bites) |
| Diagnostics | microscopy (blood smear, thick drop) |
| Therapy | antimalarials |
| MeSH ID | D010961 |
Malaria is the most serious parasitic infection in the world. It occurs in the tropical zone and is one of the diseases that are transmitted by vectors - mosquitoes.
Epidemiology[edit | edit source]
Risk of malaria infection
- Southeast Africa, Asia, Amazon;
- does not occur in Europe, Australia, the Arctic, Antarctica and most of North America;
- does not occur above 2000 m above sea level.
- occurrence always focal;
- endemic areas in Czech republic in the years 1920–1950, 215 cases;
- worldwide: 1.5–3 million deaths / year, incidence: 300–500 million / year (500 inhabitants / 10,000).
Etiology[edit | edit source]
Vector[edit | edit source]
- Mosquitoes of the genus Anopheles - about 60 species, transmitted only by females;
- the most important A. gambiae ( Plasmodium falciparum ), lays eggs in water;
- in Asia, species lay eggs in rice fields;
- mosquitoes of the genus Anopheles also occur in South Moravia.
Parasite[edit | edit source]
- Parasite: Plasmodium spp . - there are 5 species ( P. vivax , P. falciparum , P. ovale , P. malariae , P. knowlesi );
- protozoa, spores (apicomplexia)
- belongs to the blood apicomplexia - has an apical complex - an invasive apparatus enabling IC penetration;
- intracellular development in hepatocytes or erythrocytes ;
- transmitted by insects, they do not form any stages resistant to the external environment.
Life cycle[edit | edit source]
Plasmodia life cycle
- Developmental forms of Plasmodia
- sporozoite - a terminal stage of development in the carrier, infectious to humans;
- merozoite ;
- immature sexual stage - gametocyte - terminal stage of development in humans, infectious for mosquitoes.
- Cycle
Mosquito sucks blood from humans (erythrocytes contain gametocytes) → gametocytes settle in the digestive tract of mosquitoes, body cavity and salivary glands, develop into sporozoites (sexual phase of division has taken place) → mosquito sucks humans again → sporozoites enter into blood → to the liver, in the liver it changes into merozoites (asexual phase of division) → blood → attacks erythrocytes → they multiply in them until erythrolysis occurs → some merozoites change into gametocytes → mosquito sucks again → the cycle is repeated.
Stages of development in humans[edit | edit source]
- Hepatic phase - EE (extraerythrocytic), 10–14 days, sporozoites - 15–60 minutes in the bloodstream, invasion into hepatocytes (in P. falciparum and vivax the infectious dose is only 10 sporozoites ), penetrate fenestrations or Kupffer cells;
- in Disse's space, they attach to hepatocytes and penetrate;
- asymptomatic phase, no immune response develops;
- protected against complement by circumsporozoite protein in the blood, loses it after penetration into the hepatocyte;
- inside the hepatocyte - the sporozoite rounds, grows, the nucleus repeatedly divides (›1000), the cytoplasm gets segmented between the nuclei - schizogonia ;
- so-called hypnozoites - sporozoites that remain in the liver and do not divide, clinical symptoms are only when the immunity is reduced;
- return to the blood, entering the erythrocytes;
- blood phase - erythrocyte phase;
- the merozoite must enter the erythrocytes within 30 seconds of entering the blood, otherwise it dies;
- in the erythrocyte it enlarges, rounds ( ring stage ), divides, the cytoplasm is segmented between the nuclei, in one erythrocyte - there can be up to 20 merozoites, which are released by the rupture of the erythrocyte;
- merozoites enter other erythrocytes;
- the length of development in the erythrocyte varies by species;
- Plasmodium malariae - one cycle - 72 hours ;
- Plasmodium falciparum , vivax , ovale - 48 hours ;
- gametocytogenesis - formation of gametocytes, some merozoites do not divide, but transform into gametocytes;
- lasts 2-3 days in the blood, temporarily taken up in capillaries.
Plasmodium falciparum[edit | edit source]
- The causative agent of tropical malaria , found in tropics and subtropics, where the temperature does not fall below 20 ° C;
- the most severe - in non-immune individuals: if untreated, it is lethal;
- liver phase - does not form hypnozoites, up to 30 thousand merozoites in one hepatocyte, plasmodia do not remain in the liver after completion → infection is not recurrent;
- erythrocytic phases - able to infect all stages of erythrocytes, erythrocytes do not enlarge, sticky growths on their surface;
- up to 30% of erythrocytes, "rings" in peripheral blood, gametocytes;
- erythrocytes attach to the endothelium, placenta, formation increases (capillary clogging at higher developmental stages);
- protection of erythrocytes from destruction in the spleen;
- attachment to CD36, ICAM-1, placental chondroitin sulfate → cerebral malaria, in grav.
Plasmodium vivax[edit | edit source]
- Tertiary malaria (three days) (according to the length of the erythrocyte multiplication phase);
- the tropics, mostly higher temperature areas, are not in West Africa;
- liver phase - forms hypnozoites - begin to develop after a week but also after years, the cause of relapses (2x – 4x);
- erythrocyte phase - infects only reticulocytes (Duffy +), erythrocytes enlarged, but not sticky, in the peripheral blood parasitemia - corresponds to parasitemia throughout the circulation;
- Schiffner dotting;
- in peripheral blood all developmental stages.
Plasmodium ovale[edit | edit source]
- It infects erythrocytes without Duffy antigen (Duffy-), a three-day malaria (West Africa).
Plasmodium malariae[edit | edit source]
- The cause of four-day malaria (quarter) - slower development in mosquitoes and humans;
- liver phase - does not produce hypnozoites;
- erythroid phase - infects only old erythrocytes, persists in the blood for several decades,
- in one erythrocyte - 6-12 merozoites;
- low parasitemia, sudden activation.
Clinic[edit | edit source]
Video in English, definition, pathogenesis, symptoms, complications, treatment.
Malaria attack[edit | edit source]
- Induced at the time of erythrocyte breakdown and merozoite release;
- the attack is repeated after one cycle (thermal paroxysm) - directly proportional to the length of the cycle (in P. falciparum the population is not as synchronized as in P. ovale and P. vivax );
- 72 hours of development in erythrocytes → fourth day erythrocyte breakdown - fever fourth day = quarter ;
- 48 hours → fever third day = tertiary ;
- after rupture of the erythrocyte - merozoites, but also waste products of plasmodia are released:
- malarial pigment ( hemozoin ) - degradation product of Hb , phagocytosed by monocytes , inhibits their function with toxic iron → immunosuppression;
- malarial toxin ( GPI ) - released from the merozoite membrane, activates macrophages and T-lymphocytes → TNF-α production (pyrogen, NO production - CNS inhibitory neurotransmitter → deep coma).
Clinical picture of malaria[edit | edit source]
- Fever first irregular, then in cycles - tertiary and quarter;
- before the onset of fever, chills, then delusional states ;
- hepatosplenomegaly , hemolytic anemia ;
- tropicana - life threatening!
- symptoms of imported tropicany - irregular fever, persistent headache, arthralgia, shoulder pain, loose stools;
- it must be kept in mind by all those with a fever who have lived in the malarial area.
- Uncomplicated malaria (tertiary)
- originators - Plasmodium vivax , Plasmodium ovale ;
- benign malaria;
- incubation for 2-3 weeks, after 2-3 days of non-specific symptoms - febrile paroxysms;
- seizure after 48 hours;
- cold stage: 15-60 minutes, cold dry skin, cold limbs, fast pulse, chills, headache, paleness
- hot stage: 2-6 hours, fever 40-41 ° C, intense headache, flushing, fever, very intense sweating → hypovolemia;
- relapse.
- Plasmodium malariae (quarter)
- good prognosis.
- Tropical malaria - tropicana
- non-specific flu-like symptoms for several days;
- continuous fever, irregular;
- microcirculation disorders - DIC , multiorgan failure;
- severe anemia, metabolic acidosis, renal failure, pulmonary edema, hypoglycaemia, shock, spontaneous bleeding, hyperpyrexia;
- cerebral malaria - comatose state , impaired consciousness, convulsions;
- travel history! Quick diagnosis - very quickly it can turn into a very serious illness!
Diagnosis[edit | edit source]
Plasmodium in blood smear
- Travel history - ask about prophylaxis, the mode of transport (it is possible to get infected even when changing at the airport);
- direct detection of peripheral blood plasmodia on stained slides, collection at any time during infection, immunochromatographic methods , PCR ;
- microscopy - finds species identification, determines developmental stages, determination of parasitaemia, presence of hemozoin, is fast, cheap, we can monitor the effectiveness of drugs;
- Giemsa-Romanovski staining.
Treatment[edit | edit source]
- Quinine - severe tropical malaria, effective against all species, does not affect hypnozoites;
- chloroquine - effective against P. vivax , P. ovale , P. malariae , there is resistance throughout Africa;
- primachin - anti-relapse therapy (against hypnozoites);
- mefloquine - against the tropics;
- vaccination - insufficient effectiveness;
- natural resistance - sickle cell disease, ovalocytosis.
Prophylaxis and prevention[edit | edit source]
Malaria prevention is an integral part of the fight against rising malaria imports into the Czech Republic. The malaria vaccine does not yet exist . Malaria prevention can be divided into 3 groups:
- Exposure prophylaxis: use of repellents and insecticides, fumigation, use of mosquito nets, use of nets in windows and doors, wearing white loose clothing with long sleeves and trousers.
- Chemical prophylaxis: involves the use of antimalarials before, during and after a stay in an endemic area. Mefloquine, chloroquine, proguanil, atovaquone and doxycycline are used as antimalarials in prophylaxis.
- "Stand-by therapy": if a person travels to an area with a low risk of malaria or plans to stay in the endemic area for a very long time, it is possible to take an antimalarial for "emergency treatment" instead of (long-term) prophylactic use of antimalarials , ie. have an antimalarial with you and start taking it immediately if you have any symptoms or suspicion of malaria.
Comment:
- Plasmodium vivax and Plasmodium ovale - tertiary agents.
- Plasmodium malariae - the causative agent of the quarter.
- Plasmodium falciparum - the cause of tropical malaria (tropics).
- Plasmodium knowlesi - the cause of malaria in macaques in SE Asia; however, the disease has already been reported in humans.
- bad air italian: "mal aria"
Links[edit | edit source]
Related Articles _ _ edit source ][edit | edit source]
- Blood-borne infections
- Trypanosoma cruzi
- Vaccination
External links _ _ edit source ][edit | edit source]
- Malaria by Osmosis - video with English subtitles on youtube.com
References _ _ _ edit source ][edit | edit source]
- DOSTAL, Vaclav. Infectious diseases. 1st edition. Prague. 2003.
- BENEŠ, Jiří, et al. Infectious medicine. 1st edition. Galén, 2009. 651 pp. ISBN 978-80-7262-644-1 .
- STEJSKAL, Frantisek. Lecture on "Tropical and travel medicine". Department of Infectious Diseases, First Faculty of Medicine, Charles University and FNB, 2011.
- CHALUPA, Pavel. Internship in infectious medicine. Department of Infectious Diseases, First Faculty of Medicine, Charles University and FNB, 2011.
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