Elias K. Saliba

Rodents as reservoir hosts of cutaneous leishmaniasis in Jordan

Rodents were collected from endemic foci of cutaneous leishmaniasis in Jordan, either by flooding their burrows with water or using Sherman traps. Of the 170 jirds (Psammomys obesus) collected, 39 (23%) had Leishmania amastigotes in one or both ears. Although cultures of ear biopsies from the infected animals were all positive, cultures made using biopsies from their noses, livers or spleens were all negative. The infected jirds were encountered in seven of the nine areas studied. Biochemical characterization of six isolates from P. obesus, using cellulose acetate electrophoresis of six enzymes (glucose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, malic enzyme, phosphoglucomutase, phosphoglucoisomerase and fructokinase) showed that the jird isolates were isoenzymatically identical with two Jordanian human Leishmania isolates and reference isolates of L. major but differed from reference strains of L. tropica. None of the other rodents caught (Meriones libycus, M. crassus, M. tristrami, Allactaga euphratica and Gerbillus spp.) yielded Leishmania parasites, confirming that P. obesus is the major reservoir host of cutaneous leishmaniasis in Jordan.

Incrimination of Phiebotomus papatasi as vector of Leishmania major in the southern Jordan Valley

he status of sandflies as vectors of cutaneous leishmaniasis in the southern Jordan Valley was investigated during 1992. Sandflies were collected from domestic habitats and from burrows of Psammomys obesus. Of 686 Phlebotomus papatasi females collected from burrows, fourteen harboured promastigotes in their guts. On the other hand, none of 1446 P.papatasi females collected from domestic habitats were found infected. The highest infection rate (5.5%) was recorded in November at the end of the sandfly season. Six leishmanial stocks isolated from P.papatasi females were typed by cellulose acetate electrophoresis using the six enzymes G6PDH, 6PGDH, PGI, PGM, FK and ME. Five of the leishmanial stocks were identical to a Leishmania major reference strain (MHOMISU/73/5‐ASKH). The sixth isolate was a 6PGDH variant of L.major. These findings present the first direct evidence of the role of P.papatasi as a vector of L.major in Jordan.

Intestinal cestodes of stray dogs in Jordan

Five species of cestodes namelyEchinococcus granulosus, Taenia hydatigena, Taenia pisiformis, Taenia ovis andDipylidium caninum were recovered post mortem from 120 out of 173 stray dogs collected from the 5 governorates of Jordan during the period June 1979 to November 1980. Twenty-five of the examined dogs (14%) were found to be infected withE. granulosus, 79 (46%) withT. hydatigena, 14 (8%) withT. pisiformis and 5 (3%) withT. ovis. Dipylidium caninum was encountered in 33 (19%) of the examined dogs and infection with this parasite was significantly higher in males than in females. The parasites, except forD. caninum which was encountered in the ileum, were almost exclusively recovered from the duodenum and the jejunum. Single, double and triple infections with those cestodes were recorded.

Cutaneous leishmaniasis in Jordan: biochemical identification of human and Psammomys obesus isolates as Leishmania major

As part of a series of epidemiological and ecological studies of leishmaniasis in Jordan, we have made functional studies of four isolates from human lesions and from ear lesions of three field-collected Psammomys obesus. Primary isolates were subcultured, frozen stabilates prepared and BALB/c mouse infectivity experiments initiated. Each mouse was inoculated with 4-8 x 10(4) promastigotes into a hind footpad. Quantitative evaluation of the footpads showed enlargement three to four weeks postinoculation. Amastigotes were readily identified in smears from footpad lesions and promastigotes in culture. At 47 days, liver and spleen samples grew out promastigotes. Biochemical characterization of these seven isolates was made by isozyme analysis using cellulose acetate membrane electrophoresis of fructokinase, phosphoglucose isomerase, phosphoglucomutase, aspartate aminotransferase, malate dehydrogenase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Reference isolates used for comparison were Leishmania major, L. tropica minor, L. donovani, L. aethiopica and L. m. mexicana. All seven Jordan isolates showed enzyme electromorphs identical to L. major, confirming our ecological/epidemiological studies that P. obesus is a major reservoir for human cutaneous leishmaniasis in Jordan.

The endemicity of Leishmania tropica (zymodeme MON-137) in the Eira-Yarqa area of Salt District, Jordan

The endemicity of cutaneous leishmaniasis (CL) caused by Leishmania tropica was ascertained in a focus of the disease around Eira and Yarqa in Salt District, Jordan. This focus is about 10 km to the east of another focus of CL, where L. major is the causative agent. As CL occurs sporadically in the study area, with nine cases diagnosed between 1993 and 1995, it is probably zoonotic. Each case had one or two lesions and most lesions were on the face. Isoenzymatic electrophoresis showed that all the parasites isolated in the Eira-Yarqa focus and identified to zymodeme level belonged to zymodeme MON-137 and therefore differed from all the L. tropica isolates identified in other regions of Jordan. Eight species of Phlebotomus (P. alexandri, P. major, P. sergenti, P. papatasi, P. perfiliewi, P. jacusieli, P. canaaniticus and P. arabicus), two members of the Sergentomyia dentata group and S. tiberiadis and S. taizi were collected in the focus, using castor-oil traps. The epidemiological significance of the sandflies collected is discussed.

Serodiagnosis of cutaneous leishmaniasis in Jordan using indirect fluorescent antibody test and the enzyme-linked immunosorbent assay

The usefulness of IFAT and ELISA, in the detection of antibodies to cutaneous leishmaniasis (CL) in Jordanian cases was studied. Serum samples were collected from three groups of confirmed or putative CL patients (n = 100), 132 healthy blood donors, 10 patients with pulmonary tuberculosis (TB), and 16 patients with typhoid fever (TF). Antigens for both tests were prepared from promastigotes of a Leishmania major isolate. At a serum dilution of respectively 1:16 and 1:100 both IFAT and ELISA had a sensitivity of 81%, whereas in the healthy control group their specificities were 95 and 96%. Maximal titers in the 37 parasitologically-proven cases were 1:128 in IFAT and 1:800 in ELISA. Antibodies were detected in about 50% of the 42 cases that had negative parasitological tests but had typical lesions with IFAT-titers up to 1:64 and ELISA titers up to 1:400. However, antibodies were detected in 19% of the 21 clinically-suspected cases of CL with maximal titers of 1:32 in IFAT and 1:200 in ELISA. A variation in antibody level was detected in the treated and the non-treated patients who were followed up for few months after diagnosis. One serum specimen taken from a patient with TB and two sera taken from patients with TF cross-reacted with Leishmania antigens in both IFAT and ELISA. This false positivity could be eliminated by absorption of these sera with their homologous antigens. There was no significant relationship between antibody level and duration of infection with CL. On the other hand, a significant relationship between antibody level and number of CL lesions was found. Although both tests would be useful for detection of circulating antibodies in cases suspected of having CL, especially in those having several lesions, IFAT is recommended for use in Jordan for its simplicity and rapidity.

Cutaneous leishmaniasis in Mowaqqar Area, Amman Governorate, Jordan

At least 193 cases of cutaneous leishmaniasis occurred in eight villages of Mowaqqar area, Jordan, between December 1982 and April 1983. Peak transmission of the disease is thought to have taken place in late summer 1982. Approximately 67% of the cases were below 15 years of age and the lesions seen were of the dry type. The sand jird, Psammomys obesus, and the sandfly, Phlebotomus papatasi, the potential animal reservoir and vector of the disease respectively, were found in the affected area. Furthermore, Leishmania amastigotes were seen in smears from ears of seven out of 11 jirds collected from the area suggesting the zoonotic nature of the disease there.

Epidemiology of common parasitic infections of the skin in infants and children

Members of three taxonomic groups—protozoa, helminths, and arthropods—cause parasitic infections of the skin. Protozoans cause trypanosomiasis and leishmaniasis, whereas cutaneous larva migrans and cercarial dermatitis are attributed to infections with certain helminths. On the other hand, cutaneous myiasis, tungiasis, scabies, and allergic and toxic reactions are caused by arthropods. These conditions, their significance, and their recent epidemiological developments, are reviewed in this article. The term “parasite” is derived from the Greek parasitos, to denote an uninvited person who has no place at the table but sits aside and receives leftovers. It refers usually to an animal or animallike protistan that lives on (ectoparasite) or in (endoparasite) another animal. In this animal-to-animal association, the parasite is benefited while the other animal, normally referred to as the host, is harmed, and the association is termed parasitism. The host unwillingly provides the parasite with a relatively stable biotic environment where nutrients, shelter, or both are provided. The host, however, does not sit idle but fights back, mainly through tissue reactions, digestive enzymes, and cellular or humoral responses. It is postulated that the longer the evolutionary relationship between the parasite and the host, the more adapted they are to each other.1 The degree of association between the parasites affecting the skin and their hosts varies. Some spend their whole life cycle in the skin as is the case with Sarcoptes scabiei, but others come in contact with the host for a very short period of time as is the case with a female mosquito that comes to take a blood meal within a minute. In between these two examples, there are many parasites that vary in the duration of their association with the hosts. The parasites that affect the skin of infants and children are many and belong to either of the following three groups:

Humoral response of Meriones libycus to experimental infection with Leishmania major

The humoral responses of laboratory-reared jirds (Meriones libycus) to inoculation with various doses of Leishmania major were determined. The animals were inoculated intradermally with 10(2), 10(3), 10(5) or 10(7) promastigotes of a strain of L. major originally isolated from a Jordanian patient. The jirds were then bled at various intervals throughout the 26 weeks of the study, and the sera checked, by IFAT, for antibodies to homologous parasites. There were no detectable humoral responses in the animals inoculated with 10(2) promastigotes each or in parasite-free controls but a positive response was apparent in each of the other jirds. The animals given 10(3) promastigotes each required 3 months to become IFAT-positive whereas those given 10(5) and 10(7) parasites only needed 4 and 2 weeks, respectively. More than 50% of the animals inoculated with 10(3) parasites each developed strongly positive sera 2 months post-infection, whereas > 50% of the animals inoculated with 10(5) or 10(7) parasites each had strongly or very strongly positive sera 4 and 2 weeks post-inoculation, respectively. The data indicate that, in M. libycus inoculated with L. major, the time required for the humoral response to develop and its intensity are both dose-related.