Plasmodium ovale - Clinical manifestations, Epidemiology, Reservoir, Transmission, Prevention, Control, Treatment
Clinical manifestations of Plasmodium ovale
Plasmodium ovale causes ovale malaria or mild tertian malaria
the incubation period is 16-18 days
Plasmodium ovale infection is less severe in comparison to other species of Plasmodium
relapse is also less frequent than P. vivax
recovery is spontaneous
malarial fever occurs every 48-50 hours
Malaria paroxysm
shivering and cold followed by fever which can last from 2 hours to 6 hours
fever can reach as high as 40.6°C (105°F)
other symptoms accompanying fever include dry skin, headaches, nausea, and vomiting
finally, the fever subsides with the patient sweating heavily
Malarial fever
caused by rupture of mature schizonts from the infected host liver cells
In cases infected by P. vivax and Plasmodium ovale, schizonts are released every 48 hours, thus malaria fever occurs every 48 hours
enlarged spleen and anemia are also associated with children
Relapse
feature of P. vivax infection
caused by the activation of hypnozoites in the liver cells
the relapse rate is at 50% within 5 weeks (short-term relapse) or 5 years (long-term relapse) from the initial syndrome
the type of relapse depends upon the strain of Plasmodium ovale infecting the individual
Epidemiology of Plasmodium ovale
Plasmodium ovale is less prevalent with restricted distribution. The parasite is endemic to Ethiopia and is mainly found in tropical Africa, principally on the west coast.
Parts of China, the Far East, South East Asia, and South America also have reported cases of malaria.
Reservoir, Source of Plasmodium ovale
Man is the reservoir for Plasmodium ovale.
Transmission of Plasmodium ovale
Like other Plasmodium species infecting humans, Plasmodium ovale is transmitted by an infected female Anopheles mosquito.
Prevention, Control of Plasmodium ovale
The prevention and control of Plasmodium ovale infection are based on
successful treatment of infected individuals
reduction of transmission by controlling mosquito population especially around housing by eliminating breeding places, spraying oils and chemicals in breeding sites
using mosquito nets while sleeping, and netted windows in endemic areas
wearing protective clothing
use of mosquito repellants
chemoprophylaxis
Treatment of Plasmodium ovale
In uncomplicated cases, both chloroquine (for erythrocytic stages) and primaquine (for hypnozoites) are used to treat Plasmodium ovale infection.
Complicated cases of Plasmodium ovale are treated the same way as complicated P. falciparum infections.
Treatment of complicated Plasmodium ovale infection is based on
specific antimalarial chemotherapy
suppurative therapy
Specific antimalarial chemotherapy
Although such a drug is not yet available, antimalarial drugs are designed to destroy:
- all asexual forms of parasites in the blood
- hypnozoites to prevent relapse and extra-erythrocytic forms
- gametocytes to cease transmission of infection
Antimalarial drugs function by inhibiting the growth of malarial parasites by increasing the internal pH of parasites by concentration within acid vesicles of a parasite as well as inhibiting the utilization of hemoglobin and metabolism of the parasite.
some antimalarial drugs are:
- common: chloroquine, amodiaquine, chloroguanide, pyrimethamine, quinacrine hydrochloride, primaquine, proguamil, quinine
- newer drugs are used to treat chloroquine-resistant Plasmodium: artemisinin and its derivatives, mefloquine, sulfonamides such as sulfadoxine
Supportive therapy
supportive therapy and treatment of complications of malaria are important aspects of the management of malaria infection. These supportive treatments include:
cooling blankets and antipyretics to treat hyperthermia
electrolyte and fluid balance to maintain cardiac output, renal perfusion, and to prevent fluid overload
anticonvulsants to treat seizures in cases of cerebral malaria
for pulmonary edema, incubation and assisted ventilation takes place
in cases of hypoglycemia, parenteral glucose infusion is required
blood transfusion to treat severe anemia
exchange blood transfusion to treat hyperparasitemia in cases of
more than 15% of parasitemia
more than 5% parasitemia and cerebral malaria
evidence of organ dysfunction