Makindo Medical Notes.com

The risk is highest from dusk to dawn because sand flies typically feed (bite) at night and during twilight hour. Amphotericin B is now the treatment of choice due to resistance to pentavalent antimony

About

• Three forms Cutaneous (CL) Mucocutaneous (MCL) and Visceral (VL)
• Spread by infected sand flies which live on the walls of mud huts and other dwellings (Sandfly - genus Lutzomyia in the New World and Phlebotomus in the Old World)
• The infectious organisms are the protozoans of the leishmania family
• Found in Central America, South America, Africa, India, the Middle East, Asia, southern Europe, and the Mediterranean

Mechanism of infection

• Promastigotes are phagocytosed by macrophages of the reticuloendothelial system
• Once inside the macrophage they shed their flagella and become amastigotes that multiply by binary fission.
• Macrophages use nitric oxide production as an innate mechanism for killing Leishmania but the organisms block this
• If the infected cells rupture, the infection spreads to other macrophages and is carried throughout the body.

Transmission

• Spread by infected sand flies which live on the walls of mud huts
• They are most active in twilight, evening, and night-time hours (from dusk to dawn) - use netting and insect repellents
• Sand flies do not make noise; they are small and bites may go unnoticed.
• Causes Painless ulcer weeks/months after visiting an endemic area
• Lesion pain and pruritis may be present but is not typical.
• Regional lymphadenopathy and nodular lymphangitis can be noted
• Lesions can lead to localised scarring
• Mucosal lesions can cause nasal destruction

Manifestations

• Cutaneous Leishmaniasis
  • Mexico, Central America, South America, Middle East, Asia, North Africa, Southern Europe.
  • Species responsible for Dermal leishmaniasis grow best at lower temperatures than core temperature
  • Amastigotes multiply in dermal macrophages near the site of inoculation, typically on the arms, legs, face or ears. to form nodules or ulcers
  • Skin sores: US soldiers in Baghdad who have caught it call it the Baghdad Boil!
  • Skin changes can be mistaken for leprosy and patients can and did end up in leper colonies
  • Diagnose from slit skin smears which are taken from the raised edge of the CL ulcer or centre of the nodule
• Mucocutaneous leishmaniasis
  • As above but mainly seen in South America
  • Painless destruction of the nose and then nasopharynx, palate, uvula, larynx and upper airways
• Visceral leishmaniasis
  • The most severe form is visceral leishmaniasis which is frequently fatal
  • Species that cause visceral leishmaniasis to grow at core temperatures and the incubation period can be up to 2 years but usually 8 months
  • Leishmania donovani, Leishmania infantum and Leishmania chagasi are disseminated throughout macrophages of the reticuloendothelial system
  • Widespread organ involvement with fever, weight loss, and an enlarged spleen more than liver

Investigations

• Anaemia, low WCC and Low platelets and low albumin and raised gamma globulins
• Patients are vulnerable to uncontrolled bleeding, secondary bacterial pneumonia, tuberculosis or dysentery, or other infections such as cancrum oris.
• Diagnosis from Amastigotes (Leishman-Donovan bodies) in bone marrow aspirate
• Tissue scraping showed amastigotes within macrophages
• Treated patients can go on to develop Post-kala-azar dermal leishmaniasis and remain reservoirs of infection
• If normal PT time and Platelets > 40 then a splenic aspirate can be performed for culture and smear which will show donovan bodies

Advice on CDC website

• Stay in well-screened or air-conditioned areas as much as possible. Avoid outdoor activities, especially from dusk to dawn, when sandflies are the most active. When outside, wear long-sleeved shirts, long pants, and socks. Tuck your shirt into your pants.
• Apply insect repellent on uncovered skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents are those that contain the chemical DEET (N,N-diethyl-meta toluamide). The concentration of DEET varies among repellents. Repellents with DEET concentrations of 30-35% are quite effective, and the effect should last about 4 hours. Lower concentrations should be used for children (no more than 10% DEET). Repellents with DEET should be used sparingly on children from 2 to 6 years old and not at all on children less than 2 years old.
• Spray clothing with permethrin-containing insecticides. The insecticide should be reapplied after every five items of washing.
• Spray living and sleeping areas with an insecticide to kill insects. (Sandflies are particularly susceptible to insecticides)
• If you are not sleeping in an area that is well screened or air-conditioned, use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with permethrin. The permethrin will be effective for several months if the bed net is not washed. Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes. Fine-mesh netting (at least 18 holes to the inch; some sources say even finer) is needed for an effective barrier against sand flies. This is particularly important if the bed net has not been treated with permethrin. However, it may be uncomfortable to sleep under such a closely woven bed net when it is hot.