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Leishmaniasis

Leishmaniasis takes different forms in humans depending on the species of parasite causing  the infection. The most common forms are cutaneous leishmaniasis, which causes skin sores  and visceral leishmaniasis which affects internal organs. The parasites are spread by the bite  of the female phlebotomine sand flies.  

Geographical distribution (populations at risk)

Parasites of the species Leishmania cause human disease in nearly 100 different countries  over five continents. The disease mainly affects poor people in Africa, Asia and Latin America.  It is associated with malnutrition, population displacement, poor housing, weak immune  system and lack of resources. More than 90% of global cases of VL occur in six countries:  Bangladesh, Brazil, Ethiopia, India, South Sudan and Sudan. The ten countries with the  highest estimated case counts of CL are: Afghanistan, Algeria, Brazil, Colombia, Costa Rica,  Ethiopia, Iran, Peru, Sudan and Syria, which together accounts for 70 to 75% of global  estimated incidence. Today, more than 350 million people at risk with annual reports of  500,000 cases of visceral leishmaniasis (VL) and 1.5 million cases of cutaneous disease. 

Transmission

The sand flies that transmit the parasite are smaller than typical mosquitoes about one third  the size or even smaller. In the abdomen of the sand fly the parasite is found in its flagellated  promastigote form once injected into the human it changes to morphology to form the  amastigote stage.

Pathology

Leishmaniasis encompasses multiple clinical syndromes, including the cutaneous, mucosal  and visceral forms of the disease. The disease symptoms are dependent on the species of  Leishmania (see table) and generally appear few weeks or months of the sand fly bite,  although for VL symptoms may not be apparent for years following the initial bite.  The parasite infects the macrophages of either the dermis, the naso-oropharyngeal mucosa,  or throughout the reticuloendothelial system leading to the respective pathologies shown  above. In all cases Leishmania infection can range from asymptomatic to severe illness. The  parasite interferes with antigen presentation and cytokine-signalling and infection. Cutaneous  and mucosal leishmaniasis can cause substantial morbidity, including severe secondary  infections and visceral leishmaniasis can be life threatening. Infection is substantially more  serious when patients are coinfected with HIV. 

Future trends

Since 2007 because of the huge impact of the disease, the World Health Assembly has  adopted a resolution on control of leishmaniasis (WHA60.13), urging Member States where  leishmaniasis is a substantial public health problem to undertake actions to deal with the  major factors underlying the failure to control the disease. The resolution also requested the  WHO Director-General to take actions at different levels to reduce the burden of the disease. 

References

http://www.who.int/gho/neglected_diseases/leishmaniasis/en/ accessed 15th March 2014  http://www.cdc.gov/parasites/leishmaniasis/epi.html last accessed 15th March 2014

Further information

CDC_Centers for Disease Control and Prevention http://www.cdc.gov/dpdx/leishmaniasis/index.html World Health Organisation http://www.who.int/csr/resources/publications/CSR_ISR_2000_1leish/en/

Neglected Infectious Diseases

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© IP Research Consulting 2014
Leishmaniasis