November 2007

Leishmaniasis

• Introduction
• Epidemiology
• Risk for travellers
• Transmission
• Signs and symptoms
• Treatment
• Prevention
• References
• Further information
• Links

Introduction

Leishmaniasis is an infection caused by a protozoan parasite of the genus Leishmania, of which there are more than 20

sub-species. Leishmaniasis is transmitted by the bite of the

female sand fly. The organism is found in regions of tropical

Africa, Central and South America, the Mediterranean, central

and East Asia and southern Europe.

Clinical syndromes in humans are cutaneous and visceral

leishmaniasis. Cutaneous leishmaniasis is usually caused by

L. tropica and L. major and by members of the L. mexicana

complex and the Viannia subgenus. Visceral leishmaniasis

(also known as Kala-Azar) is usually caused by L. donovani,

L. infantum and L. chagasi.

 Epidemiology

Global Epidemiology

Leishmaniasis is endemic to more than 80 countries and is an

important public health concern with a global incidence of

1.5 – 2 million cases each year [1].

More than 90% of the cases of cutaneous leishmaniasis (CL)

occur in Afghanistan, Algeria, Brazil, Iran, Pakistan, Peru, Saudi

Arabia, and Syria; 90% of visceral leishmaniasis (VL) occurs in

Bangladesh, Brazil, India, Nepal, and Sudan [2]. An increase in

leishmaniasis has been observed; for example, the annual

number of cases of CL reported in Brazil increased from 21,800 in 1998, to 40,000 in 2002 [2]. An important factor in this increase has been population migration. In Manaus, Brazil, urbanisation has resulted in suburbs being built on the edge of the rainforest, placing human populations in close proximity to animal reservoirs of leishmaniasis that include opossums, sloths, and anteaters [1].  

In the poorer suburbs of Middle Eastern countries such as

Afghanistan, Iran, Turkey and Syria, population density is high

and sanitary conditions are poor, providing ideal breeding

grounds for sandflies. As a result there has been a progressive

increase in the number of cases of CL reported from Aleppo in

Syria. It is estimated that approximately 270,000 persons are

currently infected in Kabul, Afghanistan [1]. 

Leishmaniasis in travellers from England, Wales, and Northern

Ireland

In 2004, there were 50 laboratory reports of leishmaniasis, the

highest annual number reported since 1990 [3] and an increase

of 32% compared to 2003 (38 reports). In 2005, there was a

further increase of 16% (58 reports) [4]. Since 1996, the annual

number of reported cases, although small, has increased by an average of 28% every year, as illustrated in the figure. In 2004 and 2005, there was also an increase in reports where the Leishmania organism was not identified and, therefore, it is not possible to say whether they were cutaneous or visceral

infections.

Figure. Laboratory reports of leishmaniasis by clinical

expression, England, Wales, and Northern Ireland: 1996 - 2005                    

 

 

 

 

 

 

 

 

 

 

Data from the Health Protection Agency, Centre for Infections

It is presumed that all cases of leishmaniasis reported in the

United Kingdom (UK) are acquired abroad, as leishmaniasis

does not occur naturally in the UK.

In 2005, of the 26 reports of CL, 21 had travel information; nine

stated travel to Central America (seven to Belize, one to

Guatemala, and one to Costa Rica and Nicaragua), seven

travelled to Afghanistan, four to South America (one each to

Bolivia, Colombia, Guatemala, and Guyana), and one to

Pakistan. Of the six reports of VL, five had travel information; one each travelled to Afghanistan, the Balkans and Spain,

Mediterranean basin, Pakistan, and Turkey. Of the 26 unknown leishmaniasis reports, four had travel information; one each

travelled to Afghanistan, India, Belize, and Portugal [4].

Between July 2004 and June 2005, 33 cases in military

personnel were laboratory confirmed as Leishmania major [5].

Twenty cases had served in northern Afghanistan, 19 were on

exercise in Belize and four had returned from Iraq. It is likely that some personnel had served in all three places prior to their diagnosis so it is not possible to say exactly where their

infections were acquired. Similarly, between August 2002 and February 2004, 522 confirmed cases of CL were reported in

United States’ military personnel, the majority of whom had

returned from Iraq [6].

Risk for Travellers

Adventure travellers, missionaries, and soldiers who travel to

areas of risk, particularly to rural or jungle areas are at risk of cutaneous disease [7]. A review of 42 patients with CL at the

Hospital for Tropical Diseases in London, found that jungle

travel was one of the main factors for transmission [8].

VL is rare in travellers; however imported cases in the UK have occurred following travel to the Mediterranean [9]. The risk of

clinical illness with VL is greater in those with HIV infection.

Cases of VL and HIV co-infection are well-documented in

southern European countries including Spain, Italy, and France

[10].

Transmission

Leishmaniasis is a zoonosis in which humans are accidentally infected, although during epidemics, humans may play a part in maintaining the transmission cycle [11]. Mammals, including

dogs, foxes, and rodents, are the usual reservoirs for

Leishmania and the female phlebotomine sand fly is the vector.

Sand flies, contrary to what their name suggests, are not found

on beaches. They are usually found in forests, the cracks of

stone or mud walls, or animal burrows. The sand fly

predominantly bites between dusk and dawn and usually stays

close to the ground. Approximately 800 species of sand fly have

been described, of which 70 belonging to the genus

Phlebotomus or Lutzomyia are known to transmit leishmaniasis

[11].

A female sand fly requires a blood meal in order for her eggs to develop and mature. She transmits the promastigote form of the protozoa (carried in the salivary glands) to a human during

feeding.

In rare cases, VL has been transmitted congenitally and via

blood transfusion.

Signs and Symptoms

CL presents as skin lesions that develop weeks or months after infection. They can vary in appearance from a classic round ulcer

with a beefy red granulating base and raised margin, to nodules or papular scaling lesions. Regional lymphadenopathy may be present. Untreated, these lesions persist for several weeks.

Diagnosis is made by slit skin smear of the lesion, with Giesma staining and microscopy. A specialist parasitology laboratory may also be able to culture and speciate the organism.

Many cases of VL are sub-clinical. Those causing clinical

symptoms follow an acute, sub-acute, or chronic course after an incubation period of weeks or months; life-threatening disease may develop with symptoms of fever, hepatosplenomegaly, anaemia, thrombocytopenia, and hypogammaglobulinaemia. Diagnosis is made by detecting Leishmania parasites in stained slides or cultures of a biopsy sample or tissue aspirate.

 

Treatment

Patients should be referred to a specialist tropical disease unit

for diagnosis and treatment of all forms of leishmaniasis

depending upon the form of the disease. There are several drug treatments available including oral, parenteral, and topical medications. These are chosen based on the form of

leishmaniasis and the infecting species and after careful

specialist evaluation.

Prevention

There is no vaccine available for leishmaniasis. Travellers

should be advised on the need for insect bite avoidance

measures, particularly between dusk and dawn.

Sand flies are small enough to pass through a standard

mosquito net; however, if the net is impregnated with permethrin it will usually be effective in preventing the flies from going

through it.

References

1. World Health Organization. Urbanization: an increasing risk factor for leishmaniasis. Wkly Epidemiol Rec. 2002;77:365-70.

2. Desjeux P. Leishmaniasis : current situation and new perspectives. Comp Immunol Microbiol Infect Dis. 2004;27:305-18.

32. Health Protection Agency (HPA). Illness in England, Wales, and Northern Ireland associated with foreign travel – a baseline report to 2002. London: HPA; 2004. Available at http://www.hpa.org.uk/publications/PublicationDisplay.asp?

PublicationID=78.

43. Health Protection Agency (HPA). Foreign travel-associated illness England, Wales, and Northern Ireland – 2007 report. London; HPA: 2007.

5. Health Protection Agency. Cutaneous leishmaniasis in the UK Armed Forces. Commun Dis Rep CDR Wkly [serial online] 2004 [cited 7 April 2006]; 15(42): News. Available at http://www.hpa.org.uk/cdr/archives/archive05/News/news4205.

htm#leish.

6. Centers for Disease Control and Prevention. Update: cutaneous leishmaniasis in US military personnel – southwest/central Asia – 2002-2004. Morb Mort Wkly Rep 2004;53: 264-5. Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5312a4.htm.

7. Scwartz E, Hatz C, Blum J. New world cutaneous leishmaniasis in travellers. Lancet Inf Dis. 2006;6:342-9.

8. Scarisbrick JJ, Chiodini PL, Watson J et al. Clinical features and diagnosis of 42 travellers with cutaneous leishmaniasis. Travel Med Infect Dis. 2006;4:14-21.

9. Malik ANJ, John L, Bryceson ADM, Lockwood DNJ. Changing pattern of visceral Leishmaniasis, United Kingdom, 1985-2004. Emerg Inf Dis. 2006;12:1257-9.

10. Alvar J, Cañavate C, Gutiérrez-Solar B et al. Leishmania and Human Immunodeficiency Virus coinfection: the first 10 years. Clin Micro Rev. 1997;10:298-319.

11. Leishmaniasis. In Cook GC, editor. Manson's Tropical Diseases 21st ed. Philadelphia: Saunders; 2003.

Further information

Centers for Disease Control and Prevention. Health Information for International Travel 2008. Elsevier Inc. Atlanta. Available online

http://wwwn.cdc.gov/travel/yellowBookCh4-Leishmaniasis.aspx

Lawn SD, Whetham J, Chiodini PL, et al. New world mucosal and cutaneous leishmaniasis: an emerging health problem among British travellers. QJM 2004;97:781-8.

Links

World Health Organization leishmaniasis website.

http://www.who.int/leishmaniasis/en/

Special Programme for Research and Training in Tropical Diseases

http://www.who.int/tdr/diseases/leish/diseaseinfo.htm