Clinical lectures and common diagnosis of malaria

2021-04-13 11:28 AM

Malaria is a blood-borne infectious disease, caused by the parasite Plasmodium, which is passed from sick to healthy people by the mosquito Anopheles.

Clinical lectures and common diagnosis of malaria

Outline malaria

Define

Malaria is a blood-borne infectious disease, caused by the parasite Plasmodium, which is passed from sick to healthy people by the mosquito Anopheles, a locally endemic disease that can cause epidemics. The disease is clinically characterized by fever to a fever with 3 phases: burning, heat, and sweating; fever is periodic and often accompanied by anemia, splenomegaly. The clinical picture of malaria is very diverse with the following forms: Cold parasite bearing, primary, recurrent, typical common, malignant malaria, hemorrhagic malaria.

Epidemiology

Pathogens

The malaria parasite is a unicellular, family Plasmodiidae, class Protozoa, species of Plasmodium. There are 4 species of malaria parasites in humans: P. falciparum, P. vivax, P. ovale, P. malariae; particularly P. malariae is found in large African monkeys.

The development cycle of the malaria parasite has 2 stages: the liver stage (the pre-cavernous stage) and the blood stage (the cavernous stage).

In Vietnam, the two most common parasites are P. falciparum and P. vivax; In addition, P. malariae is also encountered, but more rarely, P. ovale is being determined. The rate of P. falciparum is higher than that of P. vivax in the mountainous and southern coastal areas from Phan Thiet upwards; P. vivax predominates in the plains and coastal areas with brackish water from Phan Thiet upwards. In Vietnam, P. falciparum has been resistant to Chloroquine since 1961, and has become polymorphic to slow sulfonamide, pyrimethamin, fansidar, malaria tablets II, and even quinine efficacy has decreased.

Inoculum

Malaria patients and cold parasite carriers. Patients with primary malaria are the source of the disease since the cytosol in the blood (from day 10-14 with P. falciparum and from day 3 with P. vivax). Patients with recurrent malaria are more likely to transmit earlier. The cold parasite carrier is usually a person living and infected with the parasite since childhood in malaria endemic areas, the body has a part of immunity, the rate of carrying the cold parasite often increases with age in the severe malaria area. .

Transmission route

The disease is transmitted by blood through the vector of disease is mosquito, rarely can be transmitted through blood transfusion.

The three main vectors for disease transmission in Vietnam are: An. minimus, An. dirus, An. sundaicus.

Vectơ phụ: An. subpictus, An. jeyporiensis, An. maculatus, An. aconitus, An. sinensis, An. vagus, An. indefinitus.

An. The indoor minimus shelter during the day is distributed throughout the mountainous and hilly areas of the country, in the thin forest, the forest edge, the average level is below 800 m, mainly 200-400m, with slow flowing water.

An. dirus daytime shelter completely outside, distributed from the 18th parallel onward, in dense forest, flat terrain.

An. sundaicus shelter during the day indoors, found in the brackish coast of the South.

 An. minimus and An. dirus is present from 18-19 hours to 5-6 am, burned from dusk, active in the middle of the night.

All three main vectors are also sensitive to many insecticides (malathion, fenitrotion, sumithion, permethrine, deltamethrine, icon, vector). Particularly An. minimus has shown an increase in tolerance to permethrine and An. sundaicus increased stamina with the vectron. An. minimus has the phenomenon of staying out of the house more.

Period of transmission:

The patient remains the source of transmission for as long as there is a cell in the blood. Patients with non-radical treatment may be the source of transmission for 1-2 years for P. falciparum and 1.5-5 years for P. vivax.

Mosquitoes infected with the malaria parasites can transmit the disease for a lifetime.

Stored blood infected with the malaria parasite can transmit the disease for at least 1 month.

The malaria season depends on the growing season of the malaria mosquito and human activity. In the North of Vietnam, the malaria season usually peaks in April-May and September-October (early and late rainy season); Particularly in June-July and August, there are often floods, Anopheles larvae are underdeveloped; In cold months, the temperature is <20 ° C, and mosquitoes decrease. In the South, the temperature is over 20 ° C all year round , so malaria is present all year, and develops a lot in the rainy season.

Sense of the body

People of any age can become infected. Immunity in patients infected with malaria parasites is "Presence" and no cross immunity. Therefore, after treatment, it is easy to get re-infection if still in malaria endemic areas. However, for people living in malaria areas, the disease often manifests mildly or in the form of cold parasites.

The typical clinical form of malaria

Primary malaria

Malaria is manifested for the first time in patients, often seen in people newly entering malaria or children from 4 months to 2 - 4 years old in malaria-endemic areas.

The clinical manifestations of primary malaria are continuous fever of 39 - 40 0 C or fluctuating fever, overlapping fever (2-3 peaks in a day), anemia syndrome and splenomegaly are rare. Diagnosis of primary malaria is relatively difficult, based on epidemiology and malaria parasite testing

Malaria in the primary stage

Malaria in the primary stage is malaria in the first 6 months. Thus, primary malaria includes both primary malaria and recurrent malaria within the first 6 months. Therefore, the manifestation of malaria in the primary stage of malaria can be primary or recurrent

Malaria recurs

Recurrent malaria is malaria that occurs in patients who have been infected with the parasite and have had primary malaria for more than 6 months. Recurrent malaria in patients who have been previously treated but have not cleared the parasites of malaria in the blood (due to drug-resistant parasites or underdosing) is called near relapse or P. malaria. vivax without taking a narcotic in the liver (hypnozoite) is called distant relapse.

Features of recurrent malaria are:

Fever becomes a typical episode with 3 stages and has a distinct cycle: Fever comes on suddenly with chills lasting from 15 minutes to 1-2 hours, followed by heat lasting 2 - 4 hours and body temperature peaked at 40 - 410C, eventually sweating and the temperature gradually decreased to normal.

Along with the typical fever in patients with recurrent malaria, there are usually manifest symptoms such as: enlarged liver, spleen, and over time, the bigger and stronger the liver and spleen. Anemia is the most common symptom, especially in patients with frequent recurrence of malaria. In addition, there may be some other symptoms such as yellowish mucosa, slight systolic murmur at the tip of the heart, dark skin, dark lips.

Implementing the quadrants

Epidemiological factors

Patients who are in endemic malaria, or have a history of malaria, or have just left the malaria area less than 1.5 years with P. falciparum, 3-4 years with P. vivax.

Clinical characteristics

A fever has 3 phases, cyclic.

Swollen liver and spleen.

There are manifestations of anemia.

Test

Red blood cells are decreased, white blood cells are normal or decreased.

The blood clonal malaria parasite is positive.

Differential diagnosis

Diagnose malaria with primary infection

Typhoid: Primary malaria and typhoid fever both have a constant fever, lethargy, swollen liver, spleen, and white blood cells, etc. Other typhoid features: Rotating tongue, bloating abdomen, percussion, percussion, often with loose stools - warm - plum color from 2-3 weeks, anemia does not increase clearly such as malaria, white Eosinophils are usually negative, blood cultures and Widal (+).

Fever caused by mite larvae (mum fever): The fever also has a constant high fever, occurs in the rainy season, with normal white blood cells like primary malaria. Fever differs in that there are specific ulcers with painless, non-itchy black-brown scaly, enlarged lymph nodes in the area of ​​the ulcer, erythrocytes are not clearly reduced, complement combination reaction and indirect immunofluorescence with antigens specific (+) [Weil felix OXK (OX Kingsbury) has relative value].

Dengue hemorrhagic grade I: Dengue hemorrhagic grade I is easy to confuse with primary malaria because of fluctuating fever, leukocytes also decrease. Dengue hemorrhagic grade I differs in that: Usually only 3 to 7 days fever and then return to normal, the skin and mucous membranes are clearly congested, the test of pinching the skin or ligation is positive, there is a long blood clotting at the needle of the needle, bleeding time is usually long, platelets usually decrease, erythrocytes do not decrease but tends to increase due to hemostasis, increased hematocrit, positive erythrocytic reaction (HI).

Respiratory virus infection (influenza virus, Adeno): The mucous membrane is clearly congested, often coughing, accompanied by inflammation of the nose, throat, and upper respiratory tract, no anemia, an average fever of only 3-5 days.

Distinguish recurrent malaria

With some infections, fever also becomes a daily fever, even chills, sweating.

Sepsis.

Urinary tract infections.

Inflammation of the bile ducts.

Liver abscess, tuberculosis.

Specific biological diagnosis

Detection of malaria parasites in peripheral blood (routine technique).

Fingertip blood collection and staining: Seamless on a glass slide with 1cm2 thick round and 1 thin drop (250 - 450 mm2), let dry, fix the thin drop, and destroy the erythrocytes in thick drops, dye May Grunwalld Giemsa, uncle Consider using new Giemsa - no residue, and neutral pH water.

Thick-drop smear for quick detection and counting of malaria parasites.

Use a thin smear to determine the type of parasite.

Averaging 20 minutes per slide (according to WHO). Conclusion is negative only when 100 to 200 microscopic fields have been detected on thick droplets (or at least> 50,000 RBCs per thin drop). A positive conclusion is found only when the asexual form is found in erythrocytes.

Evaluate the density of parasites on thick drops

10 parasites per 100 fields: (+) (1 plus).

100 parasites per 100 fields: (++) (2 plus).

10 parasites on 1 field: (+++) (3 plus).

100 parasites per 1 field: (++++) (4 plus).

Count the number of parasites in 1 mm3 of blood: Count the parasites in parallel with the leukocyte count on the microscopes, stop to the 200th leukocyte; Calculate the number of parasites per 1 mm3 of blood.

 In case of suspected death due to malaria, a large spleen needle can be used to take blood for testing right after the patient's death.

Quantitative Buffy Coat - Wardlaw and Levine (QBC)

Staining parasitic erythrocytes with Acridin, centrifuging, to focus the parasitic erythrocytes, and then viewing under fluorescent glasses. This technique is used in cases where it is necessary to determine the cause of malaria, but the parasites are too few and cannot be detected by routine techniques. The QBC does not allow enumeration and elimination, unless P. falciparum is present.

Malaria antibody detection techniques include

Indirect Fluorescence Method (IFAT): Positive 7-10 days after infection, titer can be reached at the acute period, this titer increases or decreases if reinfection continues. happened or not. This method is often used to select blood samples taken into the bank.

Passive or indirect erythrocyte agglutination (IHA) method. The downside of this method is that it can be negative for the newly infected person, but it is long-term positive for some parasitic antigens after 6-8 years after the cure.

Enzyme-binding immuno-adsorption (ELISA) and radiological immunity (RIA): Currently, ELISA and RIA are being widely used in retrospective research and field epidemiological investigations; The specific value depends on the purity and specificity of the antigen.

Technology to detect parasitic antigens

In recent years, there have been tests to detect circulating specific antigens of P. falciparum based on the use of monoclonal and polyclonal antibodies (such as Parasight F. test ...), but because of parasitic antigens. Usually persists in the blood for a while after the parasite has ceased and this test does not help identify the parasite, the diagnostic value of this test has decreased.

Biomolecular detection test (PCR ...)

The development of molecular biotechnology has provided a number of new tests such as polymerase chain reaction (PCR) to help diagnose parasitic strains, identify low-level parasitic infections (5-10 parasites). parasites / 1 ml of blood). Also helps to define vectors. Despite the new technique mentioned above, the classic technique of finding parasites from the fingertip blood with an optical microscope is still completely valuable in disease diagnosis and treatment research.

Points to pay attention to in diagnosing malaria

In malaria areas, or for people from malaria to healthy areas: Whenever there is a fever, it is necessary to have a blood test to find the cause of malaria; In suspected cases, treatment should be tried with malaria drugs.

A clinical case is similar to malaria, but the malaria parasite (-) and no other cause is found: It is possible to diagnose malaria clinically and try the treatment of malaria drug.

In the case of malaria parasites (+), but clinically only a few symptoms suggest malaria or suggest another unspecified disease if parasite 1 plus (+), need to re-check the parasite. and continue searching for the disease, if the parasite 2-3 plus (++, +++) may be malaria developing atypical.

The case has been identified as another disease, but there is a malaria parasite in peripheral blood:

If the malaria parasites are few, only 1 plus (+): It is possible that a person is carrying the malaria parasite and is infected with another disease.

If the malaria parasite has 2 plus or more: It is possible that a malaria co-infection with another disease.

In the malaria area, when encountering a case of long-term fever, using all the malaria drugs (artemisinin, artesunat, quinin, mefloquine ...) still cannot cut the fever, in the first 7 days, there is no parasite. In peripheral blood, it should not be easily diagnosed as persistent malaria caused by resistant parasites, but must look for other diseases (tuberculosis, infection ...).

Related articles:

Malaria WHO

Malaria Wikipedia