Epidemiology of Malaria, Modes of Transmission of Malaria

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Epidemiology of Malaria: Modes of Transmission of Malaria:

Human malaria is transmitted by the female anopheles mosquito. 60 species of this mosquito have been identified as the vector for malaria. The transmission is through a bite of an infected female Anopheles mosquito. The mosquito mostly bites during dust and dawn hours. The mosquito becomes infected when it bites a patient with malaria infection. The mosquito sucks the gametocytes from the infected person. The gametocytes proceed with their sexual cycle and the sporozoites occupy the salivary glands of the infected mosquito. After the infection, the mosquito still remains alive. When it bite bites human being for the blood meal, which it requires to nourish its eggs, it releases the sporozoites into the blood stream of human, thus transmitting the infection.

Other modes of transmission:

Blood transfusion (Transfusion malaria):

This is majorly common in endemic areas.-from the time of malaria infection; the donor may remain infective for many years.

Most infections of this nature occur when the transfusion of blood kept for less than six days. And very minimal in transfusion of blood kept for a period more than two weeks. Frozen plasma has not been known to transmit malaria.

Mother to the developing fetus: (Congenital malaria)

Intrauterine transmission of mother to the unborn child: the placenta becomes densely infested with the disease causing parasite. This mode of transmission is mostly common with the first pregnancy, in non-immune individuals.

Needles stick injury:

This type of transmission occurs accidentally among drug addicts who share needles and syringes.

Descriptive Epidemiology of Malaria:Eco-epidemiological Zones:

African Savannah malaria: (mesoendemic or holoendemic)

Fringe malaria (Africa): highland or desert seasonal unstable or periodic.

Valleys or Global plains: various breeding sites, various vectors site:

Malaria Treatment:

An early diagnosis and treatment of malaria can stop it from growing into a severe condition which can be fatal.

Mild malaria can be cared for within homes but the caregiver and the patient should be careful on the following:

The frequency and dosage of the medication.

Vomiting after medication needs more treatment.

Drugs used for the treatment of malaria:

Doxycycline-

Side effects-vomiting, abdominal pain, nausea

Avoid in use on pregnant mothers and children below 8 years.

Halofantrine-treats all 4 species of malaria

Side effects-diarrhoea, rash, itching, coughs Avoid taking with meals.

Treatment of severe malaria:

Treat convulsions with Diazepam

Give quinine intravenously

Treat anemia with ferrous phosphate (tablets):

Prevention of Malaria:

Chemoprophylaxis against Malaria:

A course of tablets given to migrants and travelers to prevent malaria when travelling from non endemic to endemic areas:

Personal Protection and Selective Vector Control Methods:

Use of insecticide-treated mosquito nets,

Personal protection measures –body repellents and coils

Insecticide spraying

Role of the health worker – early diagnosis.

Focal Nature of Malaria:

Urban conditions: transmission linked to focal breeding sites

Rural conditions: transmission linked with the proximity to breeding sites of mosquitoes.

River systems, stable water bodies, and rice paddies

Endemicity of Malaria:

• Holoendemic: transmission occurs all the year round.

• Hyperendemic: intense, but has spans of no transmission especially during dry season.

• Mesoendemic: seasonal but regular transmission

• Hypoendemic: highly intermittent transmission.

References:

Robert Sallares (2002). “Malaria and Rome: A History of Malaria in Ancient Italy”, New York, N.Y: Oxford University Press.

Frank M. Snowden (2005) .“Conquest of Malaria: Italy”, Yale University Press.

Randall M. Packard (2007) “Making of a Tropical Disease”, The Johns Hopkins University Press; Baltimore.