All clinical manifestations of malaria are associated only with erythrocyte schizogony.
The most striking clinical manifestation of malaria is fever, which occurs only when the concentration of malaria parasites in the blood reaches a certain level. The minimum concentration of parasites that can cause fever is called the pyrogenic threshold, measured by the number of parasites in 1 μl of blood. The pyrogenic threshold depends on the individual properties of the organism and its immune state. In the course of infection, due to the development of immunity, the pyrogenic threshold continuously increases, and a person who becomes infected with malaria again becomes ill with a higher concentration of parasites in the blood than a person who becomes infected with malaria for the first time in his life. With a lifetime infection, the pyrogenic threshold is from several parasites to several tens in 1 μl; and in partially immune (migrants from malarial areas) it can be at the level of several thousand parasites in 1 μl.
At the initial stage of infection, the following periods are distinguished:
- from the moment of infection to the moment the parasites enter the bloodstream;
- primary latent period;
- from the moment of infection to the threshold for detection of parasites in the blood – the prepatent period, or parasitological incubation (subpatent parasitemia);
- from the moment of infection to the achievement of the pyrogenic threshold and the appearance of febrile paroxysms – the incubation period.
There are 4 species forms of malaria: three-day, oval malaria, four-day and tropical.
Each species form has its own characteristics. However, attacks of fever, splenohepatomegaly and anemia are typical of all.
Malaria is a polycyclic infection, 4 periods are distinguished in its course: the incubation period (primary latent), primary acute manifestations, secondary latent and relapse periods. The duration of the incubation period depends on the type and strain of the pathogen. At the end of the incubation period, symptoms appear – precursors, prodromes: fatigue, muscle, headache, chills, etc. The second period is characterized by repeated attacks of fever, for which a typical stage development is a change in the stages of chills, heat and sweat. During a chill, which lasts from 30 min. up to 2–3 hours, body temperature rises, the patient cannot warm up, limbs are cyanotic and cold, pulse is quickened, breathing is shallow, blood pressure is increased. By the end of this period, the patient warms up, the temperature reaches 39 – 41 ° C, the heat period begins: the face turns red, the skin becomes hot and dry, the patient is agitated, anxious, headache, delirium, confusion, sometimes convulsions are noted. At the end of this period, the temperature drops rapidly, which is accompanied by profuse sweating. The patient calms down, falls asleep, a period of apyrexia begins. However, then the seizures are repeated with a certain cyclicity, depending on the type of pathogen. In some cases, the initial (initial) fever is irregular or permanent.
Against the background of attacks, the spleen, liver increase, anemia develops, all body systems suffer: cardiovascular (myocardial dystrophic disorders), nervous (neuralgia, neuritis, sweating, coldness, migraines), genitourinary (symptoms of nephritis), hematopoietic (hypochromic anemia, leukopenia, neutropenia, lymphomonocytosis, thrombocytopenia), etc. After 10-12 or more attacks, the infection gradually fades, a secondary latent period begins. With incorrect or ineffective treatment, several weeks later, near (3 months), late or long-term (6-9 months) relapses occur.
Three-day malaria. Duration of the incubation period: minimum – 10 – 20 days, with infection with bradysporo zoites – 6 – 12 or more months.
Prodromal phenomena at the end of incubation are characteristic. A few days before the onset of attacks, chills, headache, lower back pain, weakness, nausea appear. The disease begins acutely. The first 5-7 days, the fever may be of an irregular nature (initial), then an intermittent type of fever is established with a typical alternation of seizures every other day. For an attack, a clear change in the stages of chills, heat and sweat is characteristic. The heat period lasts 2-6 hours, less often 12 hours and is replaced by a period of sweating. Attacks usually occur in the morning. After 2-3 temperature paroxysms, the spleen and liver increase, and are sensitive to palpation. At 2 – 3 weeks, moderate anemia develops. For this species form, near and distant relapses are characteristic. The total duration of the disease is 2-3 years.
Malaria oval. According to many clinical and pathogenetic signs, it is similar to three-day malaria, but differs in a milder course. The minimum incubation period is 11 days, prolonged incubation can take place, as with a three-day period – 6 – 12 – 18 months; From publications, the deadline for incubation is 52 months.
Fever attacks occur every other day and, unlike 3-day malaria, occur mainly in the evening. Early and long-term relapses are possible. The duration of the disease is 3-4 years (in some cases up to 8 years).
Four-day malaria. Refers to benign types of malaria infection. The incubation period is 25 – 42 days, after which there are attacks of fever with a clear alternation after 2 days. Splenogepatomegaly is weak, anemia develops in rare cases. This form is characterized by low parasitemia (even during acute manifestations) and a long course (from 4 – 5 to 40 – 50 years). All this time, plasmodiums are in the blood, where there is a sluggish process of erythrocyte schizogony. Due to the long persistence of the pathogen, a self-progressing nephrotic syndrome is formed with edema, massive proteinuria, hypertension, which often occurs in children.
Tropical malaria. The minimum incubation period is 7 days, fluctuations up to 10 – 16 days. Prodromal phenomena at the end of the incubation period are characteristic: malaise, fatigue, headache, joint pain, nausea, loss of appetite, feeling of chilliness. Initial fever is persistent or irregular in nature, initial fever. Patients with tropical malaria often do not have symptoms of an attack typical of malaria: there is no or weak chills, the febrile period lasts up to 30 – 40 hours, the temperature drops without sudden sweating, muscle and joint pains are expressed. Cerebral phenomena are noted – headache, confusion, insomnia, convulsions, hepatitis with cholemia often develops, signs of a respiratory pathology appear (phenomena of bronchitis, bronchopneumonia); abdominal syndrome (abdominal pain, nausea, vomiting, diarrhea) is quite often expressed; impaired renal function.
Such a variety of organ symptoms makes it difficult to diagnose, is the cause of erroneous diagnoses.
Duration of tropical malaria from 6 months. up to 1 year.
Persons who first encounter an infection and lack immunity can develop severe and complicated tropical malaria, its malignant form: malarial coma, hemoglobinuric fever, acute renal failure, algid form, usually associated with very high parasitemia (100,000 plasmodia in 1 μl blood).
Malaria coma – cerebral pathology in tropical malaria is characterized by rapid, rapid, sometimes lightning-fast development and a difficult prognosis. In its course, three periods are distinguished: somnolence, stupor and deep coma, the mortality rate at which is close to 100%.
Often, cerebral pathology is aggravated by acute renal failure.
An equally severe course is characterized by hemoglobinuric fever, pathogenetically associated with intravascular hemolysis. Most often, it develops in people with genetically determined enzyme (deficiency of the enzyme Gb-FD) while taking antimalarial drugs. It may result in the death of a patient from anuria due to the development of acute renal failure.
The algide form of tropical malaria is less common and is characterized by a cholera-like course.
In areas endemic for malaria, there is simultaneous infection with several types of plasmodia. This leads to an atypical course of the disease, making diagnosis difficult.
Clinic of malaria in partially immune.
Clinical manifestations of malaria in the local population of endemic areas, people who, as a result of repeated reinfection, acquire relative immunity, obvious symptoms of the disease are often absent or mild, parasitemia is low. Such a state of unstable equilibrium can be disturbed during various stressful events – injuries, pregnancy and childbirth, joining infections.
Malaria in children.
In countries endemic for malaria, malaria is one of the causes of high child mortality.
Children under 6 months of age born of immune women in these areas acquire passive immunity and rarely develop malaria. Most severely, often with a fatal outcome, children from the age of 6 months are sick. up to 4 to 5 years. Clinical manifestations in children of this age are peculiar. Often the most striking symptom is absent – malarial paroxysm. At the same time, symptoms such as cramps, vomiting, diarrhea, abdominal pain are observed, there are no chills at the beginning of paroxysm and sweating at the end.
On the skin – rashes in the form of hemorrhage, spotted elements. Anemia is rapidly increasing.
In children of older age groups, malaria usually proceeds in the same way as in adults.
Malaria in pregnant women.
Malaria infection has a very adverse effect on the course and outcome of pregnancy. It can be the cause of abortions, premature births, eclampsia of pregnant women and deaths.
Vaccine (schizont) malaria.
This malaria can be caused by any type of human malaria agent, but P. malariae is the predominant species.
In past years, for the treatment of patients with schizophrenia, neurosyphilis, the method of pyrotherapy was used, infecting them with malaria by introducing the blood of a malaria patient. This is the so-called therapeutic malaria.
At present, blood transfusion and syringe malaria is isolated depending on the conditions of infection with blood infected with plasmodia. The literature describes cases of acute malaria – professional infection of medical and laboratory personnel, as well as cases of infection of recipients of transplanted organs.
The viability of plasmodia in the blood of donors at 4 ° C reaches 7-10 days.
The main difference between schizont malaria is the absence of an exoerythrocytic phase of development in the liver. The incubation period depends on the volume of blood injected and the intensity of parasitemia in the donor, it ranges from 3 to 4 days (with high parasitemia in the donor) to 3 months.
It should be noted that post-transfusion malaria can occur in a severe form, and in the absence of timely treatment, give an unfavorable outcome. Diagnosing it is difficult primarily because of the lack of a doctor’s assumption about the possibility of nosocomial infection with malaria.
The increasing incidence of schizont malaria is currently associated with the spread of drug addiction.
In the treatment of such patients, there is no need to prescribe tissue schizontocides. One of the forms of schizont malaria is a congenital infection, i.e. infection of the fetus during fetal development (transplacental when the placenta is damaged) or during childbirth.
Immunity for malaria.
In the process of evolution, humans developed various mechanisms of resistance to malaria:
- innate immunity associated with genetic factors;
- acquired active;
- acquired passive immunity.
Congenital immunity may be associated with the presence in the human body of substances that damage the parasite. For example, the absence of the Duffy group antigen, which plays the role of an erythrocyte receptor for P. vivax, on the red blood cells of a large number of Africans (West African and American Blacks) makes them immune to infection with three-day malaria. The number of intraerythrocytic genetic factors of immunity include changes in hemoglobin (hemoglobin S content), deficiency of the G-6-FDH enzyme, and low ATP level. People with such genetic indicators show relative resistance to P. falciparum, P. vivax.
Acquired active immunity due to infection. It is associated with humoral restructuring, antibody production, and an increase in serum immunoglobulins. Only a small fraction of antibodies plays a protective role; moreover, antibodies are produced only against red blood cells (WHO, 1977). The immunity is unstable, quickly disappears after the body is released from the pathogen, has a species and strain-specific character. One of the essential factors of immunity is phagocytosis.
The indigenous people of highly endemic areas of tropical Africa, where the main causative agent is P. falciparum, as a result of repeated reinfection, intense immunity against parasites and their metabolic products is generated. The invasion takes place with extremely low parasitemia and the absence of obvious clinical manifestations, which is the reason for the difficult identification of parasitic carriers among the contingents arriving in Ukraine from such areas.
In highly endemic areas, children under three months of age are not infected with malaria, receiving passive immunity from a hyperimmune mother. The highest incidence of malaria in children of the second half of life is associated with the extinction of immunity. The disease in such children is characterized by a severe course and high parasitemia.
Attempts to create artificial acquired active immunity through the use of vaccines do not lose their significance. The possibility of creating immunity as a result of vaccination with attenuated sporozoites has been proved. So, immunization of people with irradiated sporozoites protected them from infection for 3-6 months. (D. Clyde, V. McCarthy, R. Miller, W. Woodward, 1975).
Attempts have been made to create merozoite and gamete antimalarial vaccines, as well as a synthetic multivariate vaccine proposed by Colombian immunologists (1987).
Complications of malaria: malarial coma, rupture of the spleen, hemoglobinuric fever.