Malaria

by Surya Swetha Palakuru

 Disease: Malaria 

Etiologic agent: Plasmodium species: P. falciparum, P. vivax , P. ovale  and P. malariae

 

Vectors: Humans and mosquitoes

 

Transmission:

 

When a female anopheles mosquito bites a person it injects the parasite into the human blood in the form of sporozoites. These sporozoites mature in the liver as schizonts later they develop into merozoites and infect the red blood cells (1). The release of parasitic wastes due to the rupture of the erythrocytes cause chills and fever (1). Some merozoites develop into gametocytes. These gametocytes were taken up by mosquitoes (1).

  

 

  

Morphology of the malaria parasite Plasmodium falciparum inside the infected erythrocyte:

1. Early Trophozoite;

2. Early Trophozoite (double infection);

3. Early Trophozoite double chromatin with a few Maurer's dots;

4. Late Trophozoite with Maurer's dots and crenated red cell;

5. Mature Schizont with merozoites and clumped pigment;

6. Macrogametocyte with bluish cytoplasm and compact chromatin;

7. Microgametocyte with pinkish cytoplasm and dispersed chromatin.

  

General characteristics of Plasmodium falciparum:

 

It is a blood borne parasite. It exists in two types of forms – Asexual forms and Sexual forms.

Asexual forms – They are usually ring shaped and 1-2 microns in size. Other forms like amoeboid and band forms also exist (7).

Sexual forms (gametocytes) – They are larger (7-14 microns) and in case of P.falciparum are banana shaped (both macro and micro gametocytes) (7).

 

Key tests for identification:

 

             Based upon the patient symptoms clinical diagnosis can be done (10).

             Malaria can be confirmed by examining the patients blood under microscope for the malarial parasite (10).

             Malaria can also be detected by antigen detection test (10). Different test kits are available in the market which detects the antigens that are released by malarial parasite (10).

             Either indirect immunofluorescence (IFA) or enzyme-linked immunosorbent assay can be used to detect the antibodies against malarial parasite (10).

 

Signs and symptoms:

 

Fever, chills, headache, nausea,(3). These symptoms appear between10 to 15days after the mosquito bite. Classic feature of malarial fever is its periodicity i.e. every other day in P.falciparum, P.vivax, P.ovale and every third day in P.malariae. Yellowing of skin, diarrhea, and vominting can be seen due to the erythrocyte destruction (3).

 

Historical information:

 

Discovery of malarial parasite is discovered by Charles Laveran in 1880 (6). Species of malaria are differentiated in 1886) by Camillo Golgi (6). Ronald Ross discovered that mosquitoes are responsible for the transmission of malaria in 1897-1898 (6). 

Phtotgraph of Ronald Ross in 1899

Ronald Ross was the first to demonstrate that a mosquito could transmit a (bird) malaria parasite.

Portrait of Laveran

Alphonse Laveran was the first to notice parasites in the blood of a patient suffering from malaria.

 

 

 

 

 

 

 

 

 

 

 

 

Eradication of malaria: “The National Malaria Eradication Program, a cooperative undertaking by state and local health agencies of 13 Southeastern states and the CDC, originally proposed by Louis Laval Williams, commenced operations on July 1, 1947. By the end of 1949, over 4,650,000 housespray applications had been made. In 1947, 15,000 malaria cases were reported. By 1950, only 2,000 cases were reported. By 1951, malaria was considered eradicated from United States” (6).

 

Dichloro Diphenyl Trichloroethane (DDT): DDT is synthesized by Othmer Zeidler , a chemistry student, in 1874 (6). The insecticidal property is discovered in 1939 (6).

 

Chloroquine: Chloroquine is discovered and recognized as a safe antimalarial by American and British scientists in 1946 (6). 

 

Virulence factors:

 

Malarial parasite causes disease by release of merozoites by rupture of erythrocytes which results in an immune response that leads to the symptoms like fever, chills, sweating and weakness (8). In severe falciparum infection, obstruction of microcirculation by parasitized red blood cells is responsible for the complications like cerebral malaria, acute renal failure, gastrointestinal bleeding, bacteremia etc (8). 

 

Prevention:

 

Malaria can be prevented by: 1) Avoiding mosquito bites by using mosquito repellants, mosquito nets (5).

2) Chemoprophylaxis – 2 weeks before entering to 4 weeks after leaving an endemic area (5). Chemoprophylaxis is defined as the use of medications or chemical agents to prevent a disease.

 

Control and treatment:

 

Chloroquine, Mefloquine or Doxycycline are used for the treatment of malaria (5). Amodiaquine in combination with sulfadoxine and pyremithamine are used to treat the disease (8). Malarial vaccines are still experimental. Now a days Artemisinin in combination with other drugs are used against resistant strains (8).

  

Local cases or out breaks:

 

Between 1963 – 1999, 93 transfusion related malaria cases have been reported in USA (8).  About 1000 cases of malaria are reported in USA each year.  In the year 2002 1337 cases were reported in USA which includes 8 deaths (8). Between 1957 – 2003, 63 outbreaks of locally transmitted mosquito borne malaria have occurred in the USA (8).

  

Global cases or out breaks:

 

Malaria is highly prevalent in Africa and Asia (especially India) where it is an endemic disease (2).

350 – 500 million cases of malaria occur worldwide (2). 1 million of them die, mostly young children in the Sub–Saharan Africa (2)

41% of the world’s population lives in malaria endemic areas (2).

In 2002 malaria was the fourth most common cause of death in children in developing countries (2). It caused 10.7% of children deaths in developing countries (2). 

In 2006, 247 million cases of malaria and 881000 deaths were estimated (9). 

 

References:

 

1. http://www.icp.be/~opperd/parasites/malaria4.htm Dec 6 2008  Plasmodium life cycle (From the Atlas of Tropical Parasites). last updated 4 Dec 1997. 12/06/2008

 

2. http://www.searo.who.int/en/Section10/Section21/Section334_4008.htm Dec 6 2008  World health organization regional office south East Asia. 2008. Last updated 9 Jan 2007.

 

3. http://www.medicinenet.com/malaria/article.htm Dec 6 2008 Charles Davis, MD, PHD. MedicineNet.com. Dec 6 2008.

 

4. http://www.dpd.cdc.gov/dpdx/HTML/Malaria.htm Dec 6 2008 Center For Disease Control and Prevention. 5 Dec 2008.

 

5. http://www.righthealth.com/Health/Falciparum_Malaria/-od-definition_adam_1%25252F0006212-s#a11 Dec 6 2008

 

6. http://www.cdc.gov/malaria/history/index.htm Dec 6 2008   Center For Disease Control and Prevention. Division of parasitic diseases. Center for Zoonotic, vector borne, and enteric diseases. Last modified Apr 23 2004.

 

7. http://pathmicro.med.sc.edu/parasitology/blood-proto.htm Dec 6 2008  Microbiology and immunology online. University of South Carolina School of medicine.  Medical microbiology. Murray. 3rd edition. pp 632-645

 

8. http://www.cdc.gov/malaria/facts.htm  Dec 6 2008 Center For Disease Control and Prevention. Division of parasitic diseases. Center for Zoonotic, vector borne, and enteric diseases. Last modified Apr 11 2007.

 

9. http://www.who.int/malaria/wmr2008/WMR08-news-summary.pdf  Dec 6 2008 World Health Organization. World Malaria Report 2008. 10 September 2008     

 

10. http://www.cdc.gov/malaria/diagnosis_treatment/diagnosis.htm#microscopic Dec 6 2008  Center For Disease Control and Prevention. Division of parasitic diseases. Center for Zoonotic, vector borne, and enteric diseases. Last modified Jun 27 2007.