Visceral leishmaniasis (kala-azar) A systemic infection caused by Leishmania donovani which occurs in tropical and subtropical Africa, Asia, the Mediterranean littoral (and some islands), and in tropical South America. Onset is frequently insidious; incubation period is 2–6 months. Enlargement of spleen and liver may be gross; fever, anaemia, and generalised lymphadenopathy are usually present. Diagnosis is usually made from a bone-marrow specimen, splenic-aspirate, or liver-biopsy specimen; amastigotes (Leishman-Donovan bodies) of L. donovani can be visualised. Several serological tests are of value in diagnosis.
Untreated, the infection is fatal within two years, in approximately 70 per cent of patients. Treatment traditionally involved sodium stibogluconate, but other chemotherapeutic agents (including allupurinol, ketoconazole, and immunotherapy) are now in use, the most recently used being liposomal amphotericin B. Although immunointact persons usually respond satisfactorily, they are likely to relapse if they have HIV infection (see AIDS/HIV).
Cutaneous leishmaniasis This form is caused by infection with L. tropica, L. major,
L. aethiopica, and other species. The disease is widely distributed in the Mediterranean region, Middle East, Asia, Africa, Central and South America, and the former Soviet Union. It is characterised by localised cutaneous ulcers
– usually situated on exposed areas of the body. Diagnosis is by demonstration of the causative organism in a skin biopsy-specimen; the leishmanin skin test is of value. Most patients respond to sodium stibogluconate (see above); local heat therapy is also used. Paromomycin cream has been successfully applied locally.
Mucocutaneous leishmaniasis This form is caused by L. braziliensis and rarely L. mexicana. It is present in Central and South America, particularly the Amazon basin, and characterised by highly destructive, ulcerative, granulomatous lesions of the skin and mucous membranes, especially involving the mucocutaneous junctions of the mouth, nasopharynx, genitalia, and rectum. Infection is usually via a super?cial skin lesion at the site of a sand?y bite. However, spread is by haematogenous routes (usually after several years) to a mucocutaneous location. Diagnosis and treatment are the same as for cutaneous leishmaniasis.... leishmaniasis
– is caused by the bacterium Yersinis pestis. Plague remains a major infection in many tropical countries.
The reservoir for the bacillus in urban infection lies in the black rat (Rattus rattus), and less importantly the brown (sewer) rat (Rattus norvegicus). It is conveyed to humans by the rat ?ea, usually Xenopsylla cheopis: Y. pestis multiplies in the gastrointestinal tract of the ?ea, which may remain infectious for up to six weeks. In the pneumonic form (see below), human-to-human transmission can occur by droplet infection. Many lower mammals (apart from the rat) can also act as a reservoir in sylvatic transmission which remains a major problem in the US (mostly in the south-western States); ground-squirrels, rock-squirrels, prairie dogs, bobcats, chipmunks, etc. can be affected.
Clinically, symptoms usually begin 2–8 days after infection; disease begins with fever, headache, lassitude, and aching limbs. In over two-thirds of patients, enlarged glands (buboes) appear – usually in the groin, but also in the axillae and cervical neck; this constitutes bubonic plague. Haemorrhages may be present beneath the skin causing gangrenous patches and occasionally ulcers; these lesions led to the epithet ‘Black Death’. In a favourable case, fever abates after about a week, and the buboes discharge foul-smelling pus. In a rapidly fatal form (septicaemic plague), haematogenous transmission produces mortality in a high percentage of cases. Pneumonic plague is associated with pneumonic consolidation (person-to-person transmission) and death often ensues on the fourth or ?fth day. (The nursery rhyme ‘Ringo-ring o’ roses, a pocketful o’ posies, atishoo! atishoo!, we all fall down’ is considered to have originated in the 17th century and refers to this form of the disease.) In addition, meningitic and pharyngeal forms of the disease can occur; these are unusual. Diagnosis consists of demonstration of the causative organism.
Treatment is with tetracycline or doxycycline; a range of other antibiotics is also e?ective. Plague remains (together with CHOLERA and YELLOW FEVER) a quarantinable disease. Contacts should be disinfected with insecticide powder; clothes, skins, soft merchandise, etc. which have been in contact with the infection can remain infectious for several months; suspect items should be destroyed or disinfected with an insecticide. Ships must be carefully checked for presence of rats; the rationale of anchoring a distance from the quay prevents access of vermin. (See also EPIDEMIC; PANDEMIC; NOTIFIABLE DISEASES.)... plague
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