Ecology and attempted control of cutaneous leishmaniasis around Jericho, in the Jordan Valley

Two recent but temporally distinct outbreaks of cutaneous leishmaniasis among foreign workers in the Dead-Sea area of Jordan

Two temporally distinct outbreaks of human cutaneous leishmaniasis (CL), as well as scattered cases of the disease, have recently been observed close to the Dead Sea, in Jordan. Each of the two outbreaks, which occurred in 2004/2005 and 2007/2008, involved a group of foreign workers who were deployed within otherwise uninhabited locations. During each outbreak, about 20% of the workers were found infected with the causative parasite. In the earlier outbreak, 61 workers were found to have skin lesions like those of CL and all but three were confirmed by culture and/or the examination of smears (40 cases) or, in the case of 18 (86%) of the 21 suspected cases found smear- and culture-negative, by PCR. In the second outbreak, the cases were only identified from their clinical manifestations and their response to antileishmanial treatment (cryotherapy). Leishmania major was identified as the cause of the 2004/2005 outbreak and some sporadic cases that occurred, in 2004, along the shores of the Dead Sea. The burrows of potential reservoir hosts were found close to the outbreak locations, frequently under the chenopod Seidlitzia rosmarinus. The two outbreaks emphasise the continuing problem posed by the CL focus in the Mid Jordan Valley and its impact on humans who move into the area. Curiously, an investigation on the socio-economic conditions of the workers during the outbreaks identified a group of 48 workers who were living in air-conditioned rooms during the 2007/2008 outbreak, among whom no CL cases were found. In contrast, 26 of a neighbouring group of 124 workers, who were all living in non-air-conditioned rooms, developed CL lesions. The role of air conditioning, and of other factors and measures, in the prevention of the transmission of the causative parasites of CL merits further investigation and the attention of the local health authorities.

Impact of phlebotomine sand flies on U.S. Military operations at Tallil Air Base, Iraq: 1. background, military situation, and development of a "Leishmaniasis Control Program"

One of the most significant modern day efforts to prevent and control an arthropod-borne disease during a military deployment occurred when a team of U.S. military entomologists led efforts to characterize, prevent, and control leishmaniasis at Tallil Air Base (TAB), Iraq, during Operation Iraqi Freedom. Soon after arriving at TAB on 22 March 2003, military entomologists determined that 1) high numbers of sand flies were present at TAB, 2) individual soldiers were receiving many sand fly bites in a single night, and 3) Leishmania parasites were present in 1.5% of the female sand flies as determined using a real-time (fluorogenic) Leishmania-generic polymerase chain reaction assay. The rapid determination that leishmaniasis was a specific threat in this area allowed for the establishment of a comprehensive Leishmaniasis Control Program (LCP) over 5 mo before the first case of leishmaniasis was confirmed in a U.S. soldier deployed to Iraq. The LCP had four components: 1) risk assessment, 2) enhancement of use of personal protective measures by all personnel at TAB, 3) vector and reservoir control, and 4) education of military personnel about sand flies and leishmaniasis. The establishment of the LCP at TAB before the onset of any human disease conclusively demonstrated that entomologists can play a critical role during military deployments.

Evaluation of a total lymphocyte proliferation assay as a diagnostic tool for cutaneous leishmaniasis

A total blood lymphocyte proliferation (TLP) assay, recently developed for cutaneous leishmaniasis (CL), was evaluated as a tool for diagnosis of CL among patients with active lesions and apparently healthy people in an endemic area of the Jordan Valley. It was found that, in patients with lesions less than 3 months old, the TLP assay appeared insensitive, failing to detect about half of the patients in whom a diagnosis of CL had been made clinically. Blood specimens from patients with lesions of at least 3 months duration showed a positive correlation in 8 out of 10 cases. With healthy people resident in an endemic area the TLP assay was positive for 15 of 20 subjects with a past history of CL, and for only 3 of 16 without such a history. With another group of patients, not residents of an endemic area but who had spent 2 weeks together in an endemic area, and with a group of drug-treated patients, the results of the TLP assay showed a similar pattern: in patients with lesions less than 3 months old the test appeared rather insensitive, but in patients with lesions of more than 3 months duration, there was a high correlation between the TLP and clinical diagnosis.

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.

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.

Leishmaniasis in Israel: reservoir hosts, sandfly vectors and leishmanial strains in the Negev, Central Arava and along the Dead Sea

The reservoir animals, sandfly vectors and strains of Leishmania from foci in the southern region of Israel were studied. The rodent host species are: Psammomys obesus, Meriones crassus and probably Nesokia indica. The vector species are Phlebotomus papatasi, which were caught at all collecting sites and Ph. sergenti, which were collected in the area of the Dead Sea and in the Central Arava. Strains of Leishmania major isolated from rodents, vectors and man were serologically and enzymologically identical with regard to their excreted factor (EF) serotypes, their malate dehydrogenase (MDH), glucose-phosphate isomerase (GPI) and glucose-6-phosphate dehydrogenase (G6PDH) enzyme variant types, but exhibited three variant subtypes of 6-phosphogluconate dehydrogenase (6PGDH). The distribution of the 6PGDH subtypes correlates with three different geographical locations. Scarcity of water is the main factor limiting the biotopes of the sandflies and the spread of leishmaniasis. The subjects discussed are the dependence of sandfly distribution on rodent-burrow depth in arid areas and the inter-relationship between the leishmanial subtypes, vectors and hosts.

Frozen stored Leishmania tropica vaccine: the effects of dose, route of administration and storage on the evolution of the clinical lesion. Two field trials in the Israel Defense Forces

The first field trial of frozen vaccine against cutaneous leishmaniasis yielded a 100% take rate and a high ulceration rate at a dose of four million units. Two further trials were designed to investigate differences in response rates on the basis of duration of storage, sex of vaccinee, vaccination dose and method of administration. 257 soliders (151 males and 106 females) were inoculated in 1978 with an isolate of Leishmania tropica major that had been stored at the temperature of liquid nitrogen for 11 months before use. Those inoculated with an intradermal jet injector and those receiving half a million units by conventional injection yielded very low take rates. For those receiving two million and one million units, no difference in response was demonstrated between males and females or between doses. The over-all take rate for these groups after six months of follow-up was 71.6% with an ulceration rate of only 23.7%. In a subsequent trial in 1979, 131 men were inoculated with one of two frozen isolates of L. tropica major that had been stored for 11 and 18 months, respectively, at doses of either two million or four million units. The take rate after 12 months of follow-up was 91% and 93% for the four and two million units dose, respectively. The corresponding ulceration rates were 39.5% and 25%. The lesions produced by the higher dose developed more rapidly than those produced by the lower dose. The ability of the parasites to produce lesions rapidly with high ulceration rates appears to decline during prolonged storage, even in the frozen state.

Leishmaniasis in the Jordan Valley II. Sandflies and transmission in the central endemic area

Cutaneous leishmaniasis in the Jordan Valley is maintained within the close association of the rodent Psammomys obesus and sandfly Phlebotomus papatasi, which appear to be the exclusive host and vector species. The incidence of the disease was similar to the distribution of Psammomys colonies in the region, i.e., the plains of light stoneless soil. An infection rate of 93% was recorded in the very common P. obesus. Other potential host species, except for Mus musculus, were scarce and no infection with Leishmania was found in them. The only Phlebotomus species caught in significant numbers was Ph. papatasi and this was also the only species harbouring leishmanial parasites, up to 56% in one sample. All Leishmania isolates from Psammomys and from Ph. papatasi were identical to those from local human cases. The density of Ph. papatasi populations in uncultivated areas was correlated with soil conditions favouring high humidity in Psammomys burrows. A very low rate of engorged females among the Sergentomyia species collected suggests that the common species, S. antennata and S. africana asiatica, are highly autogenous.