Malaria Update

The Centre for Disease Control (CDC) reports that malaria is present in the Atlantic and Pacific coastal areas of Nicaragua, but in only 6 of the 17 provinces. Although not reported in the interior, this is presumably because mosquitoes are not as prevalent at the higher elevations in the more mountainous interior, and otherwise this is likely a reporting anomaly, because mosquitoes do not acknowledge provincial borders.

Malaria in Nicaragua is due to Plasmodium vivax (P. vivax) in 95% of cases and Plasmodium falciparum (P. facliparum) in the remaining 5%. This is good news because P. vivax is chloroquine sensitive and has a good prognosis for full recovery. P. falciparum is a much more serious infection. A 2013 study in neighboring Honduras confirms that the P. falciparum in the region is still chloroquine sensitive. 

The Anopheles mosquito transmits the parasite into the bloodstream. The parasites enter red blood cells. About a week or two later, the red blood cells release thousands of parasites and inflammatory chemicals into the blood. The inflammatory chemicals include pyrogens, which cause the fever. The fever in P. vivax develops every 48 hours. The red blood cell destruction results in anemia.


The incubation period varies from 7 to 30 days.

Malaria is most severe among children 6 months to five years of age. Those over six months of age no longer have maternal immunity and those under five years have not reached full immunologic maturity. In endemic areas such as Nicaragua, malaria is the cause of up to 10% of all deaths in young children!

Parasitemia in neonates within 7 days of birth implies transplacental transmission. Babies have fever, irritability, refuse feeds, and often develop anemia, jaundice, and hepatosplenomegaly.

In younger children, the fever is usually continuous and might be very high (40°C) from the first day. The symptoms are often non-specific. Children become restless, drowsy, apathetic, and anorexic.

Older children might present with the classic periodic fever with chills and shivering. Other symptoms include generalized ache, headache, and nausea. Flu-like respiratory symptoms, with mild cough and cold are common. Vomiting is very common. Mild diarrhea with dark green mucoid stools is common. The liver might be slightly tender. Splenomegaly is classic but takes many days to develop, especially in the first attack in non immune children.

Children with partial immunity might develop only a low-grade fever, anemia, poor appetite, and malaise.

P. vivax malaria might relapse for up to 3 years.

Cerebral Malaria Cerebral malaria is due to P. falciparum and has a mortality of 25%, even with modern treatment. Cerebral malaria is most common in children 6 months to 3 years and survivors often have serious neurological sequelae such as hemiparesis. P. falciparum-infected red blood cells adhere to the walls of veins and do not freely circulate in the blood. The sequestration of these infected cells in the brain is considered a factor in cerebral malaria. In children, seizures might occur at the onset of the disease. Differentiating a febrile seizure from cerebral malaria is often difficult.

Laboratory Diagnosis The traditional method to confirm a diagnosis is microscopy of a thick blood smear stained with Giemsa. A rapid diagnostic test is now available. Neither of these options are usually available in rural Nicaragua. 

Blood smear with two RBC on right infected with P. Falciparum. 

Image courtesy of CDC. 

Treatment Since the symptoms are often non-specific, high fever in a susceptible young child requires a high index of suspicion, and in the absence of a recognized cause for the fever, empirical treatment might be necessary.

Children five years or younger should seek malaria treatment within 48 hours of the development of fever. In Nicaragua the local names for fever include calentura, fiebre, or mal de ojo.

The treatment of P. vivax is a 3-day course of chloroquine, (10 mg/kg orally up to 600 mg, then 5 mg/kg at 6 hours, 24 hours, & 48 hours after the larger first dose) followed by a 14-day course of primaquine. The primaquine is necessary to eliminate the dormant stage of the parasite in the liver.

Prevention DEET may be used to prevent mosquito bites. 95% DEET lasts up to 10-12 h and 35% DEET lasts 4-6 h.

Increased precautions are needed during the night, because Anopheles species are nocturnal. Sleeping under insecticide-treated (permethrin 0.2 g/m2 of material every 6 mo) mosquito nets is efficacious.

References
  

http://www.cdc.gov/malaria/index.html

http://emedicine.medscape.com/article/998942-overview

Torres REM et al. Efficacy of Chloroquine for the Treatment of Uncomplicated Plasmodium falciparum Malaria in Honduras. American Journal of Tropical Medicine and Hygiene. http://ajtmh.org/cgi/doi/10.4269/ajtmh.12-0671