Table The vectors and reservoirs of leishmaniasis

Type and parasite

Geographical area

Main vector

Reservoir

Visceral L. donovani (including infantile)

Mucocutaneous L. braziliensis L. guyanensis

Mediterranean, SWAsia

Central Asia China

India, Bangladesh Sudan, Chad

Kenya

Central and South America

Central and South America

Cutaneous (New World)

L. mexicana Mexico, Belize, Guatemala

Amazon Basin Peru

Cutaneous (Old World)

Mediterranean Southwest Asia

L. major L. tropica

L. aethiopica

Central Asia India

West Africa

Ethiopia

Kenya

Phlebotamus peniciosus, P. ariasi, P. major syriacus, P. longicuspis

P. major syriacus, P. smirnovi, P. longiductus P. chinensis

P. argentipes, P. papatasi P. orientalis, P. martini

P. martini

Lutzomyia longipalpis

L. wellcomi, L. L.trapidoi umbratilis,

L. olmeca

L. flaviscutellata

L. peruensis, L. verrucarum

P. papatasi P. papatasi, P. P. papatasi P. sergenti P. duboscqi P. longpipes P. pedifer sergenti

Dogs, foxes

Dogs, jackals, foxes

Dogs Humans

Wild rodents and carnivores

Dogs

Dogs, foxes

Rodents and forest animals

Forest rodents Forest rodents Dogs

Rodents, dogs, gerbils Dogs, rodents Rodents, gerbils Dogs

Dogs, rodents

Hyrax

Rodents

Fig. 15.22

The global distribution of cutaneous and visceral leishmaniasis. H, Cutaneous;

A range of reservoirs is found in this complex of diseases. In Central Asia, cutaneous leishmaniasis is a zoonosis, the gerbil being the main reservoir. In India, there is a domestic reservoir, mainly dogs, but direct human-to-human transmission also occurs. These are summarized in Table 15.6.

Transmission can also take place directly through needles and other instruments contaminated with blood of an infected person. Sadly, this is also the method by which HIV is transmitted in many developing countries.

Incubation period 2 weeks to 6 months, but can be years.

Period of communicability The untreated case can remain infectious to sandflies for up to 2 years.

Occurrence and distribution Leishmaniasis is found in Central and South America, north of the equator in Africa , in the Mediterranean, Southwest, Central and South Asia and part of China as shown in Fig. 15.22 and Table 15.6. Population movements, both of persons from endemic rural areas into towns and large man-made projects, such as dams in endemic foci, have brought an increasing number of people into contact with leishmaniasis. Also, the spread of HIV infection has made what was largely a curable condition into a persistent source of parasites for the vector sandfly and as a result, a more serious disease.

Immunity develops following infection with the parasite, but there is little cross-immunity. L. tropica has been used for a long time as an inoculum to induce a sore on a hidden part of the body so as to prevent a more disfiguring lesion developing on the face. L. major will protect against L. tropica as well as L. major lesions, and suspensions of living organisms have been prepared for this purpose. There is no cross-immunity with kala-azar and the other species of Leishmania, but an attack of kala-azar will protect against developing kala-azar in any other part of the world.

Control and prevention Cases of the disease are normally sporadic, so should be treated to prevent flies from becoming infected. Repellents and personal protection adequately protect the individual from being bitten. Sandfly nets can be used, but a more effective solution is ITMN or LLIN (see Malaria above). Because of the fragile nature of the vector, it is easily attacked with insecticides, either with a residual house spray if the vector comes indoors, or by insecticide powder blown into mammal burrows, ant hills and similar micro-habitats. A long-term solution is to alter the micro-environment, such as by the destruction of termite hills and killing of rodents. Proper control of domestic animals, especially dogs, can be effective where they are important reservoirs. Low-dose inocula and attenuated vaccines have been developed to minimize the severity of disease in some endemic areas. The concomitant problem of HIV infection has added to the seriousness of dual infection, so a simultaneous programme of STI control is required and information produced on how to avoid both diseases.

Treatment is with sodium stibogluconate or meglumine antimonate, but pentamidine or amphotericin B may be required in cases that do not respond, especially mucocuta-neous leishmaniasis. Because of the toxicity of the preparations, treatment should be undertaken in hospital. Miltefosine maybe useful in the treatment of visceral leishman-iasis.

Surveillance Outbreaks should be reported to neighbouring countries so that they can take control measures in border areas. Patients with HIV infection should be examined for reactivated leishmaniasis.

Emergency Preparedness

Emergency Preparedness

Remember to prepare for everyone in the home. When you are putting together a plan to prepare in the case of an emergency, it is very important to remember to plan for not only yourself and your children, but also for your family pets and any guests who could potentially be with you at the time of the emergency.

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