Malaria, Vivax

Malaria A protozoan disease caused in humans by four species of the genus Plasmodium (P. falcipamm (malaria, falciparum), P. vivax (malaria, vivax), P. ovale, and P. malariae) and transmitted by the bite of an infected female mosquito of the genus Anopheles. Malaria is endemic in parts of Asia, Africa, Central and South America, Oceania, and certain Caribbean islands. It is characterized by extreme exhaustion associated with paroxysms of high fever, sweating, shaking chiUs, and anemia. Malaria in animals is caused by other species of plasmodia. [nih]... 

Malaria, Vivax Malaria caused by Plasmodium vivax. This form of malaria is less severe than malaria, falcipamm, but there is a higher probability for relapses to occur. Febrile paroxysms often occur every other day. [nih]... 

Malaria is transmitted by the bite of an infected female Anopheles mosquito, one of the few species of the insect capable of carrying the human malaria parasite. The responsible protozoa ate from the genus P/asmodium of which only four of some 100 species can cause the disease in humans. The remaining species affect rodents, reptiles, monkeys, birds, and Hvestock. The species that infect humans are P/asmodium falciparum Plasmodium vivax Plasmodium malariae and Plasmodium ovale. Note that concomitant multiple malaria infections are commonly seen in endemic areas, a phenomenon that further compHcates choice of treatment. 

Plasmodium vivax, responsible for the most prevalent form of malaria (benign tertian), has an incubation period of 8—27 days (14 average). A variety seen in northern and northeastern Europe has an incubation period as long as 8—10 months. The disease can cause splenic mpture and anemia. Relapses (renewed manifestations of erythrocytic infection) can occur with this type of malaria. Overall, P. vivax is stiU susceptible to chloroquine however, resistant strains have been reported from Papua New Guinea and parts of Indonesia. Plasmodium malariae the cause of quartan malaria, has an incubation period of 15—30 days and its asexual cycle is 72 hours. This mildest form of malaria can cause nephritis in addition to the usual symptoms. It is a nonrelapsing type of malaria but the ted blood ceU infection can last for many years. No resistance to chloroquine by this plasmodium has been reported. Plasmodium ovale responsible for ovale tertian malaria, has an incubation period of 9—17 days (15 average). Relapses can occur in people infected with this plasmodium. No chloroquine resistance has been reported for this parasite. 

Four different protozoa of the genus Plasmodium -P. falciparum, P. vivax, P. ovale and P malariae - can cause malaria. P. falciparum is the most virulent, being responsible for virtually all fatal malaria cases. Humans are infected by a feeding female Anopheles mosquito (Fig. 2). The clinical symptoms of malaria are associated with the development of the parasite within human red blood cells, while the liver stages remain asymptomatic. The following dtugs (in alphabetical order) are currently in use for the treatment of malaria [5]. 

Malaria remains a major public health problem in many parts of the world, including Southeast Asia, sub-Saharan Africa and Latin America where an estimated 300-500 million people are infected. 1-3 million die of malaria every year. The etiologic agents of malaria are protozoan parasites of the genus Plasmodium. Of the four pathogens that can cause malaria in humans (Plasmodium falciparum, P. vivax, P. ovale,... 

Malaria is transmitted from person to person by a certain species of the Anopheles mosquito. The four different protozoans causing malaria are Plasmodium falciparum, P. malariae, P. ovale, and P. vivax. Drugp used to treat or prevent malaria are called anti malarial drags. Three antimalarial drugs are discussed in the chapter chloroquine, doxycycline, and quinine sulfate. Other examples of antimalarial drugs in use today are listed in the Summary Drug Table Antimalarial Drugs. 

Malaria is transmitted by the bites of the Anopheles mosquitoes which introduce into the bloodstream one of four species of sporozoites of the plasmodia (Plasmodium falciparum, P. ovale, P. vivax or P. malariae). Initial symptoms of malaria are nonspecific and may resemble influenza and include chills, headache, fatigue, muscle pain, rigors, and nausea. The onset of the symptoms is between 1 to 3 weeks following exposure. Fever may appear 2 to 3 days after initial symptoms and may follow a pattern and occur every 2 or 3 days (P. vivax, P. ovale and P. malariae). Fever with P. falciparum can be erratic and may not follow specific patterns. It is not unusual for patients to have concomitant infections with P. vivax and P. falciparum. Falciparum malaria must always be regarded as a life-threatening medical emergency. 

The distribution of the various species of malaria is not well defined but P. vivax is reported to be prevalent in the Indian subcontinent, Central America, North Africa, and the Middle East, whereas P. falciparum is predominantly in Africa (including sub-Saharan Africa), both East and West Africa, Haiti, the Dominican Republic, the Amazon region of South America, Southeast Asia, and New Guinea. Most P. ovale infections occur in Africa, while the distribution of P. malariae is worldwide.7 Most infections in the United States are reported in American travelers, recent immigrants, or immigrants who have visited... 

In an uncomplicated attack of malaria (for all plasmodia except chloroquine-resistant P. falciparum and P. vivax), the recommended regimen is chloroquine 600 mg (base) initially, followed by 300 mg (base) 6 hours later, and then 300 mg (base) daily for 2 days.3 In severe illness or falciparum malaria, patients should be admitted to an acute care unit and quinidine gluconate 10 mgsalt/kg... 

Following treatment of falciparum malaria, TW has remained well for 2 months. However, 2 days ago, he started developing fever and chills, nausea, and abdominal pain. When seen in the emergency department he has a fever of 38.4°C and complains of severe headache. Examinations of a thick and thin blood smear of the patient s blood identified P. vivax infection. TW received a course of chloroquine and primaquine. In a follow-up 2 weeks later, a repeat blood smear was negative for parasites and the patient was asymptomatic. 

When advising potential travelers on prophylaxis for malaria, be aware of the incidence of chloroquine-resistant P. falciparum malaria and the countries where it is prevalent. In patients who have P. vivax or P. ovale malaria (note that some patients can have P. falciparum and one of these species), following the treatment of the acute phase of malaria and screening for glucose-6-phosphate dehydrogenase deficiency, patients should receive a regimen of primaquine for 14 days to ensure eradication of the hypnozoite stage of P. vivax or P. ovale. For detailed recommendations for prevention of malaria go to www.cdc.gov/travel/. 

T4. Tobie, J. E., Abele, D. C., Hill, G. J., Contacos, P. G., and Evans, C. B., Fluorescent antibody studies on the immune response in sporozoite induced and blood induced vivax malaria and the relationship of antibody production to parasitaemia. J. Trop. Med. Hyg. 15, 676-683 (1966). 

Chloroquine is the drug of choice for preventing and treating acute forms of malaria caused by P. vivax, P. malariae, P ovale, as well as sensitive forms of P. falciparum. The mechanism of its action is not completely clear, although there are several hypotheses explaining its antimalarial activity. Chloroquine and its analogs inhibit synthesis of nucleic acids of the parasite by affecting the matrix function of DNA. This happens by preliminary... 

Hydroxychloroquine, like chloroquine, is also used for treating acute forms of malaria caused by P vivax, P. malariae, P. ovale, and also sensitive forms of P. falciparum. It is also effective and safe like chloroquine, although it does not have obvious advantages. The only advantage is that it is somewhat better tolerated. Its use is somewhat more limited than chloroquine. Synonyms of this drug are plaquenil, quensyl, toremonil, and others. 

Primaquine is the most effective and most toxic drug from the whole series of known 8-aminoquinolines. It is generally used for treating exoerythrocyte forms of malaria caused by P. vivax and P. ovale. It also acts on the sexual forms of the plasmodia, which die in the human body upon using this drug. 

This powerful inhibitor of dihydrofolate reductase is used for preventing and treating malaria caused by plasmodia P. vivax, P. malariae, P. ovale, including P. falciparum. 

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