Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.

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Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

Background Cutaneous leishmaniasis (CL) is endemic in Pakistan and is widely spreading. Recently, an outbreak of the disease was observed in the region. We report some new endemic areas of CL in the country.



Methods A total of 1210 cases of CL who visited our department from 1996 to 2001 are reported. Among them, 760 were residents of the Jacobabad, Larkana, and Dadu districts of Sindh province and had never previously traveled to endemic areas. These districts have never been reported/recognized as endemic for CL. Others were residents of endemic areas of Balochistan province. Diagnosis was made on clinical presentation; a giemsa-stained smear test and histopathological results. All the cases were treated with the meglumine antimoniate 600 mg/day (adults) and 15 mg/kg/day (children) intramuscularly for 20 consecutive days.



Results All the patients were aged between 2.5 months and 65 years. Three hundred and ninety-two patients were females and 368 were males. Duration of the disease ranged from 2 to 18 months. Most of the patients had a single lesion on the face and/or extremities. Clinically, the disease was classified as: dry papular type, 407 cases; dry ulcerative type, 335 cases; and wet ulcerative type, 18 cases. No cases of muco-cutaneous or visceral leishmaniasis were found during this period. Smear testing was positive in 845 cases, while 365 cases were histopathologically positive. An ultrastructural study was performed using specimens of a few of the cases. Leishmania parasites were detected in the dermal tissues as well as in the macrophages.



Conclusions We propose that the Jacobabad, Larkana and Dadu districts could be considered endemic for CL. Wet- and dry-type lesions indicate the presence of both Leishmania tropica and L. major in this tropical region.

Detection of new endemic areas of cutaneous leishmaniasis in Pakistan: a 6-year study.

Visceral leishmaniasis (VL) was first reported in Pakistan over 30 years ago from the remote north-eastern Himalayan region. Sporadic cases are now widely reported from the Northern Areas, part of North-West Frontier Province (NWFP) and Punjab Province, together with Azad Jammu and Kashmir (AJK). Two hundred and thirty-nine cases, mostly young children, have been reported in the last decade; 52% were under 2 years old, and 86% were aged less than 5 years; the male:female ratio was 3:1. In a cross sectional study of the population in 14 endemic villages, 1938 individuals of all ages were randomly skin-tested with leishmanin and 27.4% gave a positive result. The leishmanin response rate increased with age. In some areas, almost 70% of the adults over 40 years old were positive. Leishmanin positivity appeared to cluster among households (P = 0.0003), but clinical cases among households did not (P = 0.472). The leishmanin response pattern in the foci of Chilas and AJK reflected an endemic pattern of disease, whereas that seen in the Baltistan foci suggested interrupted transmission. Human sera collected in endemic villages were tested for anti-Leishmania antibodies, 580 by enzyme-linked immunosorbent assay and direct agglutination test (DAT), and another 1403, as blood samples on filter paper, were tested by DAT alone. Isolations of Leishmania were made from 15 patients, 11 from bone marrow, 3 from normal skin and one from spleen. The parasites were typed as Leishmania infantum zymodeme LON-49 (= MON-1).

Leishmania infantum in the Himalayas

Infantile visceral leishmaniasis (VL) was first reported from north Pakistan over 3 decades ago in the remote valleys of the western Himalayas. These foci were reported as being completely devoid of domestic dogs. The later emergence of sporadic cases of infantile VL in the sub-Himalayan region of the country, where dogs are abundant, enabled us to investigate the prevalence of canine disease and study its relation with disease in humans. A serological survey in dogs by direct agglutination test (DAT) and enzyme-linked immunosprbent assay (elisa) indicated that 18% (DAT) and 26.6% (elisa) harboured anti- Leishmania antibodies, with older dogs showing higher prevalence; 10% of the infected dogs had no clinical signs of leishmaniasis. Deoxyribonucleic acid (DNA) probing by 32 P-labelled Lmet 2 cDNA probe showed high sensitivity with aspirates obtained from the popliteal lymph nodes of dogs but not with skin snips. Parasites isolated from dogs in these foci were identified as L. infantum by isoenzyme characterization.

The role of dogs in the epidemiology of human visceral leishmaniasis in northern Pakistan.

Present Situation of Cutaneous Leishmaniasis in Balochistan, Pakistan

valleys in the area are at an altitude of6,000 to 10,000 feet above sea level. The most important valley is the Indus river valley. The present study relates to the area traversed by the rivers Indus and Shyok, lying between latitude 35 to 35'3°N and longitude 75'5 to 76'5°£. (Fig. I). These valleys are bounded by mountains ranging from 10,000 to 15,000 feet above sea level and the height of valleys ranges from 7,800 to 8,500 feet. The principal town of Baltistan is Skardu. The valleys of the rivers Indus and Shyok have been very important trade routes of Baltistan,. The Shyok river valley once connected the area with China through the Karakoram pass and the Indus valley connects Baltistan with Kashmir. The Baltistan population is rural, scattered, and scanty. Villages are situated at the junction of mountain streams and rivers. In between the villages the area is barren, as agriculture is only possible in areas traversed by a mountain stream out of which irrigation channels have been ingeniously constructed. The area has a long winter from October to April. The summer period is from June to August only. Mean maximum and minimum records of temperature and rainfall in respect of Skardu representative of the area under study are presented below (Ahmad 1962) (Table I). 110 I A LONGITUDINAL STUDY OF VISCERAL LEISHMANIASIS

Lari Fa

Papers

A longitudinal study of visceral leishmaniasis in northern areas of Pakistan.