Seasonality as a determinant of the efficacy of praziquantel in population-based chemotherapy: lessons from the practice.

During October-November 1991, 1356 male farmers, 18-40 years old from a village in Fayoum Governorate, Egypt, were examined for Schistosoma haematobium infection. The prevalence of infection was 22.2%. Infected farmers were treated immediately with praziquantel at the recommended dose of 40 mg/kg body weight in a single, oral dose. Twelve weeks after treatment 86/262 (32.8%) infected farmers were negative for S. haematobium eggs in urine. In another study conducted in a satellite village in the Nile Delta (Beheira Governorate) where S. mansoni infection is prevalent, all residents of both sexes between 5 and 50 years of age (n = 858) were examined for S. mansoni. The prevalence of S. mansoni was 69.0%. Infected subjects were treated with the same dose of praziquantel during January-February 94, with an overall resultant efficacy of 85.5% (471/551) and 97.2% (103/106) in 18-40 years old males 8-10 weeks post treatment. The high cure rate in the second study was probably because treatment took place 2 months after the end of the high transmission season.

The prevalence and intensity of Schistosoma mansoni infection among residents in two Egyptian villages, at two and twelve months post-treatment with 40 and 60 mg praziquantel per kg body weight at these two villages respectively.

Two different regiments of praziquantel, 40 mg/kg in a single dose and 60 mg/kg in two divided doses administered 6 hr apart for the treatment of S. mansoni infection, were compared at two villages of Beheira Governorate. All residents of both sexes between 5 and 50 yrs old from two rural communities (Farshout and Om El-Laban) participated in this study. The prevalence of S. mansoni infection was 58% at Farshout and 69% at Om El-Laban. Infected subjects received 60 mg/kg of praziquantel in two divided doses 6 hr apart at Farshout and 40 mg/kg in a single dose at Om El-Laban. Two months post-treatment, better cure rates (96% vs 85%, P < 0.001) were achieved with 60 mg/kg of praziquantel. Twelve months post-treatment the prevalence of infection (45% for both villages) increased, but remained lower than before treatment. This may indicate that transmission continued from cercariae transported by water from nearby hyperendemic areas. The prevalence and intensity of infection were higher in the younger (5-19 y) than in the older (20-50 y) age group both before treatment and one year post-treatment. The same applies to the incidence and reinfection of the treated subjects. We recommend that 60 mg/kg in two divided doses six hours apart be used for school children. For logistical reasons, the single dose, 40 mg/kg regimen, should be used for mass treatment. For better control of disease, mass chemotherapy with praziquantel as suggested above is essential for the whole endemic region rather than only for a focal area.

Intestinal capillariasis as a cause of chronic diarrhoea in Egypt.

Intestinal capillariasis in humans is caused by a nematode- Capillaria philippinensis, which infects small fresh water or brackish fish and some fish eating birds. It has occurred in areas where people eat raw fish such as the Philippines and Thailand. This paper reports a case of a women with intestinal capillariasis in Menouf, in the Nile Delta of Egypt. It is the second case to be reported from the same area of Menouf. Microscopic examination of stool revealed eggs, larvae and adult male and female worms of C. philippinensis. This was successfully treated with Albendazole.

Susceptibility of three successive snail generations from positive and negative laboratory bred Biomphalaria alexandrina from different localities in Egypt to infection with Schistosoma mansoni from Giza.

Susceptibility of snail vectors to schistosome infection varies between geographical areas, populations in the same area and among individuals in the same population. It is also affected by biological factors of which are snail size (age), number and age of miracidia exposed to water, temperature, illumination and darkness. Our preview studies indicated that snails 4-6 mm in diameter exposed to 5 freshly hatched miracidia under light and in water at 25 degrees C are optimum conditions for infection of Biomphalaria alexandria from various localities in Egypt with Schistosoma mansoni (TBRI strain maintained in hamsters). In the present study, groups of 16 snails from three successive generations from positive and negative laboratory bred B. alexandrina from Giza, Alexandria, Menoufia, Cairo and Minia were exposed to S. mansoni miracidia (TBRI Strain) from Giza under the above mentioned optimum conditions. From the 20th day infection snails were checked from cercariae shedding to estimate the prepatent period and their number from each snail light for one hour. B. alexandrina from the various localities in Egypt were susceptible to S. mansoni (TBRI strain) infection. Snails from Alexandria were the most susceptible, followed by those from Cairo, Giza, Menoufia and Minia. Snails from positive generations were more susceptible to infection than those from negative ones. However, there has been a decline in the susceptibility of snails from one generation to the next. The prepatent period for shedding of cercariae was 27 days in case of snails from positive generations and it was extended to 38 days among snails from negative ones. It can be concluded that: (1) There are different levels of susceptibility between B. alexandrina from the various localities in Egypt and infection with S. mansoni from Giza. (2) Unsusceptibility (refractory character) of B. alexandrina to S. mansoni infection could be a heritable character like susceptibility. Consequently, it would be beneficial to select actively resistant snails and mass culture them to increase the proportion of alleles for insusceptibility as a possible mean for biological control of schistosomiasis in natural population.

Amebiasis in schistosomiasis endemic and non-endemic areas in Egypt.

Stool and blood specimens were collected from each of 404 and 576 individuals at Sindbis village (Qualiubia Governorate) in the Nile Delta where schistosomiasis is endemic and El-Rashda village (New Valley Governorate) in the Western Desert of Egypt where there is no schistosomiasis; respectively. Based on the microscopical examination of stool specimens, the prevalence of infection with Entamoeba (E. histolytica and/or E. dispar which are morphologically indistinguishable) was higher at Sindbis than at El Rashda village (29.3% and 20%, respectively). At Sindbis, the prevalence of Entamoeba (both species) was 35.2% (50/142) in S. mansoni infected individuals versus 26.3% (69/262) in S. mansoni negative individuals. Serum antibodies develop only against E. histolytica but not against E. dispar infection. When serological results were considered, the prevalence of E. histolytica was 4.7% in Sindbis and 3.4% at El Rashda based on those who were positive microscopically and serologically in the two villages, respectively. In other words, only 16-17% of those who were positive microscopically can be considered infected with E. histolytica as determined serologically. However, the prevalence of E. histolytica (present or past) based on those who were positive serologically whether positive or negative microscopically was 13.4% and 12.7% at the two villages, respectively. At Sindbis, the prevalence of E. histolytica infection was lower in S. mansoni negative (8.5%) than in S. mansoni positive (16.0%) individuals. These epidemiologic data suggest that: (1) S. mansoni infection may suppress the immune response of the host and therefore, the prevalence of E. histolytica based on serological testing is probably underestimated in the S. mansoni infected people and it may be higher than in the S. mansoni negative people. (2) Serological examinations can be used in determining the true prevalence of E. histolytica (present or past infections) until a routine test for detecting E. histolytica specific antigen in stool becomes available to differentiate E. histolytica from E. dispar infections.

Vector-host-parasite inter-relationships in leishmaniasis. I. The effect of Leishmania parasites on rate of digestion of blood proteins from various vertebrate hosts by the sand fly Phlebotomus langeroni (Diptera: Psychodidae).

Protein digestion in the gut of Phlebotomus langeroni (Nitzulescu) was studied at four subsequent 24 hour intervals post feeding on human, dog (Canis familiaris), rat (Rattus rattus) and turkey (Melagris gallopava) bloods with and without Leishmania infantum or L. major promastigotes. Most of the proteins of the studied blood meals were digested within 96 hours. The percent of blood proteins digested in the first 48 hours was higher than in the second 48 hours in all cases of the studied blood meals except the normal blood of the turkey in which the ratio of the digested blood proteins in the two periods was 1:1. During the first 48 hours, the percent of the digested blood proteins was lower than normal in the presence of L. infantum in case of human and dog blood meals. The reverse was true in case of the rat and turkey blood meals in the presence of L. infantum and in the blood meals from each of the four vertebrate hosts in the presence of L. major. The significance of these findings in considering L. infantum as a natural parasite of P. langeroni in El Agamy focus was discussed.

Vector-host-parasite inter-relationships in leishmaniasis. II. Influence of blood meal from natural vertebrate hosts with and without Leishmania infantum and L. major on the proteolytic activity in the gut of Phlebotomus langeroni (Diptera: Psychodidae).

Proteolytic activity in the gut of Phlebotomus langeroni (Nitzulescu) was studied at four subsequent 24 hours intervals post feeding on human, dog (Canis familiaris), rat (Rattus rattus) and turkey (Melagris gallopava) bloods with and without Leishmania infantum or L. major promastigotes. The gut proteolytic activity increased gradually after feeding to reach a maximum at 48 hours post feeding on any of the 12 studied blood meals. In all cases, the activity declined after 48 hours and almost terminated by 96 hours. In case of normal bloods, the proteolytic activity, at 48 hours post feeding, was the highest in case of dog followed by human, rat and turkey respectively. At this time interval the activity was relatively lower in case of human and dog blood mixed with L. infantum promastigotes than in their respective normal blood. The reverse was true in all other blood meal combinations. Promastigotes were alive and active in fresh gut smears of P. langeroni fed on human, dog and rat bloods mixed with either L. infantum or L. major, throughout the digestion period (1-4 days). They were arrested in P. langeroni within the first day post feeding on turkey blood mixed with either Leishmania species. The results of the present study indicate that the kind of blood meal and the Leishmania species affect the proteolytic activity of P. langeroni. The decrease or increase of the proteolytic activity of P. langeroni has no effect on the survival of Leishmania parasites present in the gut and the kind of blood meal is responsible for their development.

Infection of laboratory bred Biomphalaria alexandrina from Giza and Alexandria governorates with Schistosoma mansoni from Giza in relation to snail size and number of penetrated miracidia.

Snail size and the number of Schistosoma mansoni miracidia penetrated are two important factors among others that might influence Biomphalaria alexandrina infection with S. mansoni. Groups of 16 snails of fixed age but of different size class (2-4 mm), (4-6 mm), (6-8 mm), (8-10 mm) and (10-12 mm) from three successive generations of positive and negative laboratory bred B. alexandrina from Giza and Alexandria governorates were each exposed to five S. mansoni miracidia (TBRI from Giza) under light and in water at 25 degrees C. After 20 days, the snails were examined for cercarial shedding to determine their prepatent periods and to estimate the number of cercariae shed from each snail under light for one hour. Other groups of snails (4-6 mm) from three successive generations of positive and negative laboratory bred B. alexandrina from these two Governorates were each exposed to 3, 5, 10, 15, 20 and 25 miracidia. Snails were checked starting from the 20th day of infection to assess whether or not they had acquired infection. The infection rate of B. alexandrina from Giza and Alexandria governorates and their generations decreased significantly as the snail size increased while it increased significantly as the number of miracidia increased. However, there has been a decline in the susceptibility of snails from one generation to the next. The prepatent period for the shedding of cercariae was long in large sized snails and from those descending from negative snails. It can be concluded that the infection rate of B. alexandriina snails is affected by snail size and the number of miracidia penetrated.

Vector-host-parasite inter-relationships in leishmaniasis. III. Impact of blood meal from natural vertebrate hosts on the survival and the development of Leishmania infantum and L. major in Phlebotomus langeroni (Diptera: Psychodidae).

Phlebotomus langeroni collected from a leishmaniasis endemic focus at Et Agamy, Alexandria, Egypt, were found to have fed on blood from man, dogs (Canis familiaris) and rats (Rattus rattus). The effect of the kind of blood meal on the development and the life-cycle of L. infantum and L. major in laboratory reared P. langeroni was therefore investigated. A membrane feeding technique was used to infect sand flies. Gut smears of infected females were examined immediately after feeding and daily for 16 days. Nectomonads and short promastigote forms of L. infantum or L. major were detected in females fed on human, dog and rat bloods at all intervals. Paramastigotes (infective stage) were present only in females fed on dog blood containing L. infantum or L. major and in those fed on rat blood containing L. major. It is concluded that among the factors influencing the Leishmania-phlebotomus relationship is the natural medium in which the parasite is present in vivo. The blood of the natural reservoir host(s) is the key factor for the development of the infective parasite form in the sand fly and P. langeroni could be considered a potential vector for transmitting L. infantum from dogs and L. major from rats and dogs but not from man. This investigation offers a new concept for the study of interactions among vector, host and parasites in Leishmania transmission.

Vector-host-parasite inter-relationships in leishmaniasis. IV. Electrophoretic studies on proteins of four vertebrate bloods with and without Leishmania infantum or L. major.

Fifty five protein bands with relative mobilities of 8,954 to 245,471 kilo Daltons (kD) were electrophoretically separated from 12 feeding media of blood from 4 natural vertebrate hosts of Phlebotomus langeroni. The feeding media included human, dog (Canis familiaris), rat (Rattus rattus) and turkey (Melagris gallopava) bloods without or with Leishmania infantum or L. major promastigotes. Protein bands were identical among the feeding media of one host's blood but varied in number (24-28 bands) and relative mobilities among the various hosts' blood. Some protein fractions were common among the various hosts blood, others were only present in two or three hosts' blood and some were restricted to one host blood and were unique for each host. This study provides data which may help in understanding why blood from different natural hosts may variably influence the life cycle of Leishmania parasite in the sand fly gut.

Identification of a misleading trypanosomatid parasite from Gerbillus pyramidum and G. andersoni in a Leishmania major endemic area in north Sinai.

During an epidemiologic investigation of cutaneous leishmaniasis at a focus in north Sinai, Egypt, between June 1989 and December 1991, 897 desert rodents were trapped and examined to identify reservoir hosts for Leishmania major. Mixed forms of epimastigotes and promastigotes were isolated in Tanabe's medium from 4 Gerbillus pyramidum and 1 Gerbillus andersoni. The 2 forms were later grown and separated as distinct cultures in Schneider's medium. The isoenzyme profile of the gerbils' promastigotes was identical to Leishmania tropica but differed from those of L. major and the gerbils' epimastigotes. The protein pattern by sodium dodecyl sulfate poly acrylamide gel electrophoresis gave no conclusive results. The Hae III restriction endonuclease analysis of kinetoplast DNA of both morphological forms confirmed their similarity and distinguished them from L. tropica and L. major. The gerbils' promastigotes were 30% broader, with a smaller nucleus than those of L. tropica. Following several subcultures, epimastigotes were found to transform to promastigotes. These observations suggest that the 2 forms belong to the genus Trypanosoma. Further studies are in progress to classify this putative Trypanosoma species whose promastigote stages display isoenzyme patterns identical to L. tropica, and which can be misidentified microscopically as Leishmania promastigotes.

Leishmania major: amastigote formation in cell-free media.

The life cycle of Leishmania consists of two distinct developmental stages: the amastigote, which is the ovoid non-flagellated form found in the vertebrate host, and the promastigote, which is an elongated flagellated form found in the gut of an infected sandfly. Following its injection into the vertebrate host by the sandfly vector, the promastigote transforms into an amastigote after entering the host macrophage. The environmental cues inducing this transformation are not fully understood. Attempts to axenically develop and cultivate amastigotes from different Leishmania species have indicated that species and sometimes even strains of the same species vary in their requirements for this process (Pan et al., 1993). The majority of the available published data on transformation pertains to New World Leishmania and provides evidence that elevation in the incubation temperature and/or acidic pH can in some cases induce amastigote formation from promastigotes.

Biological and biochemical comparative studies on Schistosoma mansoni from two localities in Egypt where S. haematobium is endemic.

The changing pattern of Schistosoma mansoni and S. haematobium distribution in Egypt is generally attributed to ecological changes caused by the construction of the Aswan High Dam. Although S. mansoni was previously restricted to Lower Egypt, it is now found at certain foci in Upper Egypt. In areas of Lower Egypt where S. mansoni and S. haematobium are sympatric, S. mansoni eggs are shed almost exclusively in the stools of patients, whereas in Upper Egypt they are more frequently shed in the urine. In spite of this difference, the eggs and adult worms obtained from hamsters infected with S. mansoni strains from each of these areas proved to be morphologically identical. Protein patterns and isoenzyme profiles of male or female adult worms of each of the two isolates, obtained from infected hamsters, also proved virtually identical. In hamsters with mixed infections of S. mansoni and S. haematobium, some S. mansoni females cross-mated with S. haematobium males and they then developed ovaries and laid eggs which were typical of S. mansoni and which were excreted from the urinary bladder. In Upper Egypt, which is predominantly a S. haematobium area, patients with established infections may have a preponderance of S. haematobium males associated with S. mansoni females. These females may then migrate to the vesicular plexus and deposit S. mansoni eggs in the urinary bladder, to be shed subsequently in the urine. The observations appear to be better explained by the phenomenon of parthenogenesis than by the production of true genetic hybrids.

Biochemical characterisation of human isolates of Blastocystis hominis.

SDS-PAGE and iso-enzyme analysis of 11 human isolates of Blastocystis hominis revealed at least two variants with different polypeptide patterns and two zymodemes, respectively. This is the first iso-enzyme and the second protein analysis to indicate strain differences in B. hominis.

Worm development in hamsters infected with unisex and cross-mated Schistosoma mansoni and Schistosoma haematobium.

Schistosoma mansoni and Schistosoma haematobium coexist in Egypt and in other areas in Africa, and people frequently are infected with parasites of both species. The effects of the interactions between worms of both sexes of the 2 species on development and egg laying were evaluated in vivo by infecting hamsters with cercariae from Biomphalaria alexandrina and Bulinus truncatus snails infected with single miracidia. In hamsters with unisex infections, male worms of both species were small. Schistosoma mansoni females were stunted and partially mature but did not contain eggs. Schistosoma haematobium females, though stunted, sometimes contained and laid small eggs, which were deposited in the liver, but few of which contained motile embryos. This suggests that unisexual infection with S. haematobium female worms produces a risk for liver damage due to egg deposition in tissues. Both S. mansoni and S. haematobium females that mated with males of the heterologous species were significantly larger than females from unisexual infections; they were sexually mature and possessed eggs in the uterus. The eggs in the liver homogenates of cross-specific infected hamsters contained fully developed miracidia that hatched in filtered pond water.

Evaluation of a twice-a-week application of 1% niclosamide lotion in preventing Schistosoma haematobium reinfection.

A randomized double-blind trial was conducted to assess the efficacy of a twice-a-week application of 1% niclosamide lotion for prevention of Schistosoma haematobium reinfection. Six hundred farmers in Fayoum, Egypt, 18-40 years of age, were treated to cure their S. haematobium infection, then randomly assigned to self-apply niclosamide or placebo lotion to their limbs, neck, and torso. Subjects were exposed to schistosomal-infested water during routine irrigation activities from April to October 1992. Three hundred fifty subjects met the inclusion criteria and completed the trial, 169 (48.3%) in the niclosamide group and 181 (51.7%) in the placebo group. The subjects assigned to the niclosamide-treated group were comparable with those in the placebo group in age (27.2 versus 27.8 years), total water contact (101.9 versus 109.0 hr), lotion application compliance (93.5% versus 90.6%), and avoidance of whole body water contact (94.7% versus 96.7%). The reinfection rate with S. haematobium was 30.8% in the niclosamide-treated group and 28.2% in the placebo group. Niclosamide lotion applied to the limbs and trunk twice a week failed to prevent S. haematobium reinfection.

Etiology of acute diarrhea among United States Embassy personnel and dependents in Cairo, Egypt.

The purpose of this study was to identify the enteropathogens causing acute diarrheal disease in Americans living in the North Africa/Middle East region during a 34-month period from February 12, 1985 to December 30, 1987 to guide preventive and therapeutic measures. Stool specimens were examined and an epidemiologic questionnaire was administered to patients with acute diarrhea at the Outpatient Health Unit of the United States Embassy in Cairo, Egypt. The subjects consisted of 126 American employees and dependents of the U. S. Embassy in Cairo, Egypt with diarrhea of less than two-weeks duration. Subjects received routine medical care administered by the U.S. Embassy Medical staff. A possible etiologic agent was detected in 41% of the subjects. Enteroadherent Escherichia coli was the most commonly isolated enteropathogen. A high degree of antimicrobial resistance was noted among the bacterial isolates, but all were susceptible to the quinolone antibiotics. Episodes of acute diarrhea occurring among American expatriates in Cairo, Egypt were primarily of bacterial etiology, but only a small portion were caused by the bacterial pathogens routinely identified in a standard clinical bacteriology laboratory. Most of the diarrheal episodes were due to noninvasive enteroadherent E. coli that may cause prolonged disease requiring antimicrobial therapy.

Identification of Trichinella isolates from naturally infected stray dogs in Egypt.

Larvae of Trichinella species recovered from the diaphragms of 2 stray dogs killed during a governmental antirabies campaign in Cairo, Egypt, were fed to white mice for production of adult worms and larvae for morphological and isoenzyme studies. Comparisons were made with reference species of Trichinella spiralis, Trichinella nelsoni, Trichinella nativa, and Trichinella pseudospiralis. Results indicated that the 2 Trichinella specimens from the dogs were morphologically and biochemically identical with T. spiralis.

Epidemiology of cutaneous leishmaniasis at a focus monitored by the multinational force and observers in the northeastern Sinai Desert of Egypt.

A longitudinal epidemiologic study of cutaneous leishmaniasis (CL) transmission was conducted between July 1989 and June 1991 in a 1,200-km2 sector of the northeastern Sinai Desert monitored by the Multinational Force and Observers (MFO), an international peace keeping mission between Egypt and Israel. The occurrence of human cases, sand fly density, rodent collection, and isolations of Leishmania confirmed only one of four surveyed locations as a significant focus of CL transmission. Phlebotomus papatasi, the only anthropophilic sand fly species encountered at this focus, comprised more than 96% of the sand fly population and attained human landing densities exceeding 100 sand flies/person/hr during 1990. Seasonal activity of this species ranged from April to November, with highest densities occurring during the period May-September. A peak promastigote infection rate of 2.4% (13 of 534) was observed in P. papatasi during July 1990. Twelve of the 60 (20%) persons at risk during the six months of intense sand fly activity at this site developed lesions consistent with CL; L. major was isolated from nine (75%) of these cases. Leishmania major infection was acquired by two of 22 (9%) sentinel hamsters used during the same period. More than 97% of the 897 wild rodents trapped at this site were desert gerbil species. Leishmania major was the only Leishmania isolated from human, sand fly, wild rodent (Gerbillus pyramidum), and sentinel hamster infections that originated at site Check point 1-Delta, the focus of CL transmission within jurisdiction of the MFO. The altered ecology of this area, created by construction of a dam, may contribute significantly to the transmission dynamics of CL at this focus.

Field trial of 1% niclosamide as a topical antipenetrant to Schistosoma mansoni cercariae.

A randomized, double-blind, placebo-controlled field trial of a topical antipenetrant lotion, 1% niclosamide, applied daily to the upper and lower limbs of farmers occupationally exposed to Schistosoma mansoni cercarial-infested water, was conducted in the Nile Delta to assess its safety and efficacy in preventing reinfection. Farmers aged 18-40 years were treated to cure their S. mansoni infections three months prior to the onset of the trial. Subjects were randomly assigned to receive niclosamide or placebo lotion that was self-applied daily for five months. A total of 186 subjects met the inclusion criteria and completed the trial. The exposure to schistosomal-infested water occurred during routine irrigation activities from June to November 1991. Stool specimens were evaluated monthly during and for two months following the lotion application period. The subjects applying the niclosamide lotion were comparable to those applying placebo lotion in age (mean 30 years for both), total water contact (184.5 hr versus 173.8 hr), reported lotion application compliance (88% versus 92%), and reported water contact involving skin exposure other than upper and lower limbs (23% versus 27%). The schistosomal reinfection rate was lower in the niclosamide group (53.3%) compared with the placebo lotion group (71.3%), (P < 0.02). Increased protection might be obtained with total body application for shorter, less intense, water contact exposures.