Sexual behaviour and HIV epidemiology: comparative analysis in France and Britain. The ACSF Group.

OBJECTIVE: France and Britain have similar size populations, yet the incidence of AIDS is threefold higher in France. The objective of this study was to compare data from two surveys recently performed in the two countries, in order to determine whether differences in sexual and drug-use behaviour could explain the different epidemiological patterns. DESIGN: Cross-sectional random sample surveys of France and Britain. RESPONDENTS: In France, 20,055 persons aged 18-69 years and in Britain, 18,876 persons aged 16-59 years were interviewed in 1990-1991. The following indicators were compared in the respondents aged 18-59 years: prevalence of homosexual experience and injecting drug use, number of sexual partners, prevalence of sexual practices, condom use and sex with prostitutes, age of sexual partners. RESULTS: Very similar results were found for the prevalence of male homosexual partnerships. Slightly higher numbers of lifetime partners were reported by French than British men, but no difference was found for recent periods. Anal intercourse and sex with prostitutes was more frequent among heterosexual French people than British people. Condom use was more systematic in Britain than in France. CONCLUSION: Only small differences were found between the two countries, although prevalence of risk indicators were higher in France. These differences combined with early development of prevention policies in Britain, together with the timing of virus introduction, may contribute to differences between the epidemics in the two countries.

The supply and demand dynamics of sexual behavior: implications for heterosexual HIV epidemics.

This article investigates the supply and demand dynamics of sexual behavior in a simple epidemiological model of heterosexual transmission of human immunodeficiency virus (HIV). The supply and demand dynamics of sexual behavior are modeled by specifying implicit sexual behavior change (ISBC) mechanisms. These mechanisms specify how males and females modify their rates of sex partner change in response to changes in the availability of the opposite sex. During an epidemic, the availability of both sexes will change owing to recruitment and mortality; consequently, implicit sexual behavior changes will be induced. These behavior changes will be independent of any explicit sexual behavioral changes that may occur as a result of intervention strategies. We investigate four different ISBC mechanisms: the two extremes of the continuum of possible mechanisms (where only one sex changes behavior), as well as two intermediate possibilities (where both sexes change behavior). The results show that the epidemiological effects of these ISBC mechanisms depend upon the transmission speed of the virus. If HIV transmission is slow, the epidemiological effects of the four ISBC mechanisms cannot be differentiated. If HIV transmission is fast, the four ISBC mechanisms differ considerably in the degree to which they modify the gender-specific rates of sex partner change, but the sexual behavioral changes occur too late to significantly decrease the cumulative number of infected persons. However, if HIV transmission is moderately fast, the four different ISBC mechanisms produce significantly different epidemics. The differences between the epidemics, produced by the four ISBC mechanisms, are magnified as the degree of asymmetry between the heterosexual transmission efficiencies increases. We discuss the implications of our results for both the future number of AIDS cases that will be observed in the "real world" and the number of AIDS cases that will be predicted from mathematical models. We also discuss the implications for studies that evaluate the causation of sexual behavior changes.

Identification of a major 72 kilodalton surface antigen in twelve isolates of Leishmania braziliensis braziliensis.

The study of the surface antigens of Leishmania braziliensis braziliensis revealed a great homogeneity among ten strains isolated from Bolivia and two reference strains from Brazil and Belize. A 72 kDa major protein, present in all L. b. braziliensis strains, was recognized by both cutaneous and mucocutaneous human sera, but was not recognized by Kala-azar and chagasic sera. No cross-reactive antigens were found among strains of Leishmania braziliensis guyanensis, Leishmania braziliensis panamensis, Leishmania mexicana amazonensis and Leishmania donovani chagasi testing these strains with hamster and human anti-L. b. braziliensis sera. Moreover, these strains possessed major antigens with molecular weights different from those of L. b. braziliensis strains. A microheterogeneity of L. b. braziliensis surface antigens was detected for the high molecular weight antigens and seemed to be related to the isoenzymic microheterogeneity.

Estimation of the size of the HIV/AIDS epidemic due to blood transfusion in France.

BACKGROUND: This study presents estimates of the number of individuals contaminated by human immunodeficiency virus (HIV) via a blood transfusion received in France before the end of 1991 and those who have developed or will develop AIDS. METHODS: The computer simulation model takes into account several possible hypotheses concerning the annual number of infected blood donations collected before the introduction of HIV screening in August 1985, those collected between August 1985 and December 1991 not excluded by the testing procedure due to the seroconversion period, the number of labile blood components elaborated from one donation, the 5-year mortality rate of blood recipients, and the incubation delay. RESULTS: Results reproducing the evolution of the reported annual number of transfusion-associated AIDS cases were selected which enabled the estimation of the number of recipients infected (between 3300 and 4300) and of the number of transfusion-associated AIDS cases (between 1600 and 1800) compared with 1300 transfusion-associated AIDS cases reported by June 1993. CONCLUSION: This methodology could be used for other countries provided information required by the model is available.

Cryptic speciation in Lutzomyia (Nyssomyia) trapidoi (Fairchild & Hertig) (Diptera: Psychodidae) detected by multilocus enzyme electrophoresis.

Lutzomyia trapidoi is the major vector of cutaneous leishmaniasis in Ecuador. In the framework of an epidemiologic study, female Lu. trapidoi sand flies were captured on human bait in La Tablada and Paraiso Escondido. Some coloration heterogeneity among the specimens caught led us to look for the existence of cryptic species using multilocus enzyme electrophoresis. In 196 specimens studied, five of seven enzyme loci proved to be variable, making it possible to check for departures from panmixia both by Hardy-Weinberg statistics and linkage disequilibrium analysis. Two discrete groups were clearly distinguished, which could be differentiated by the diagnostic locus glycerophosphate dehydrogenase. The two groups occurred in sympatry within each locality. Genetic distances measured between these two groups were consistent with values usually found between distinct species. These results suggest the existence of a least two sibling species in Paraiso Escondido as well as La Tablada. The epidemiologic relevance of these results is discussed.

Lutzomyia nuneztovari anglesi (Le pont & Desjeux, 1984) as a vector of Leishmania amazonensis in a sub-Andean leishmaniasis focus of Bolivia.

Recently, a new Leishmania amazonensis focus was described in a sub-Andean region (1,450-2,100 meters above sea level) of Bolivia. In this area, three anthropophilic sandfly species were identified: Lutzomyia nuneztovari anglesi Le Pont & Desjeux, 1984, which represented 86-99% of the captures, Lu. galatiae Le Pont et al., 1998, and Lu. shannoni Dyar 1929. Only Lu. nuneztovari anglesi was found naturally infected by flagellates (16 of 1,715 females). Three Leishmania stocks were isolated and analyzed by isoenzyme electrophoresis at 11 loci. No significant isoenzymatic differences were demonstrated between them and 7 stocks isolated from patients from the same area, and previously characterized as L. amazonensis. Moreover, in a simplified protocol, the experimental infection of Lu. nuneztovari anglesi by L. amazonensis was successful in 92% of the surviving specimens. These data are discussed in relation to the Killick-Kendrick criteria. These results strongly suggest that Lu. nuneztovari anglesi is the vector of L amazonensis at Cajuata, Inquisivi, La Paz, Bolivia.

Genetic analysis of leishmania parasites in Ecuador: are Leishmania (Viannia) panamensis and Leishmania (V.) Guyanensis distinct taxa?

In the course of an epidemiologic survey in Ecuador, the following collection of Leishmania stocks was isolated: 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either Leishmania (V.) panamensis or L. (V.) guyanensis, 2 stocks were identified as L. (V.) braziliensis, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between L. (V.) braziliensis and L. (V.) guyanensis. These data show that genetic diversity of Leishmania in Ecuador is high and that L. (V.) panamensis/guyanensis is the dominant group in this country. The genetic analysis questioned the distinctness between the two species L.(V.) panamensis and L. (V.) guyanensis, since MLEE and RAPD data did not indicate that L. (V.) panamensis and L. (V.) guyanensis correspond to distinct monophyletic lines. Population genetic analysis performed on the L. (V.) panamensis/guyanensis group favors the hypothesis of a basically clonal population structure.

Leishmaniasis in Bolivia. I. Lutzomyia longipalpis (Lutz & Neiva, 1912) as the vector of visceral leishmaniasis in Los Yungas.

A relatively high leishmanial infection rate was found in the phlebotomine sandfly Lutzomyia longipalpis collected from three villages of the Los Yungas region (Department of La Paz, Bolivia). 2,578 female sandflies were dissected. In three houses surveyed in Santa Barbara promastigote infection rates of Lu. longipalpis were 4.2, 2.2 and 3.2% respectively. Anatomical localization of the infection in the insect, and biochemical characterization of the strains indicate that the parasite belongs to the Leishmania donovani complex. The geographical area and the biotopes of Lu. longipalpis are discussed in relation to the vector-parasite relationship.

Cutaneous leishmaniasis in Bolivia. A study of 185 human cases from Alto Beni (La Paz Department). Isolation and isoenzyme characterization of 26 strains of Leishmania braziliensis braziliensis [corrected].

A clinical, serological, parasitological and therapeutic study of cutaneous leishmaniasis was carried out in a low sub-andean area (250-800 metres) of the La Paz Department, Bolivia. A team of seismic prospectors (350 workers) was surveyed for 12 months. Of 200 suspected cases of cutaneous leishmaniasis, 185 were serologically or parasitologically confirmed (incidence 52.8%). Those exposed to the greatest risk of infection were working in a virgin forest environment. Leishmanial organisms were isolated from 26 of the workers, either by in vitro cultivation or inoculation into hamsters. Isoenzyme characterization of the organisms by cellulose acetate electrophoresis showed them to be Leishmania braziliensis braziliensis [corrected]. The results of treatment of 168 patients with a pentavalent antimonial drug are also reported.

Epidemiology of leishmaniasis in French Guiana.

Lutzomyia umbratilis is confirmed as the vector of Leishmania braziliensis guyanensis, the cause of "pian bois" in man in French Guiana. Although spending most of the year in the forest canopy, this sandfly is abundant at ground level for about two weeks at the beginning of the long rainy season. The maximum number of infective bites per man per hour (3.9) was reached at the end of November 1979. Infections were found in one of seven Potos flavus, seven of 15 Choleopus didactylus and two of 19 rodents examined. C. didactylus seems likely to be the main reservoir.

A first case of cutaneous leishmaniasis due to Leishmania (Viannia) lainsoni in Bolivia.

We present the first known case of cutaneous leishmaniasis due to Leishmania (Viannia) lainsoni detected in Bolivia. The parasite was isolated from a young girl living in the subtropical region of Carrasco (900-1000 m above sea level, Caranavi Province, Department of La Paz, Bolivia). The parasite identification was confirmed by multilocus enzyme electrophoresis.

Co-infection by Leishmania amazonensis and L. infantum/L. chagasi in a case of diffuse cutaneous leishmaniasis in Bolivia.

We present the first report of a co-infection by Leishmania amazonensis and L. infantum/L. chagasi isolated in 1993 from a patient with diffuse cutaneous leishmaniasis (DCL), living in the sub-Andean region of Bolivia. This is the third reported case of DCL in Bolivia, but the first one with isoenzymatic identification of the aetiological agents involved and the first one giving evidence for a mixed infection by 2 Leishmania parasites in the same lesion.

Additional data on Trypanosoma cruzi isozymic strains encountered in Bolivian domestic transmission cycles.

We have collected in Bolivia 212 stocks of Trypanosoma cruzi from domestic transmission cycles and have assayed for nine enzyme systems (11 gene loci). Only a few different isozyme profiles exist, without recombination between them, a situation also encountered in previous Bolivian samples. The 212 stocks, combined with 207 stocks previously studied, have been analysed to uncover any spatial patterns. The frequency of heterozygous strains (2 and 2a) decreases westwards and with increasing altitude. Given that longitude and altitude are correlated with each other, it is not possible to decide which of these two geographic variables is the relevant one, or if both are. These associations might be due to climatic factors. Studies by other authors have shown, however, that heterozygous strains are rare or absent in the Amazon Basin, which is at low altitude.

Separation of Psychodopygus carrerai carrerai and P. yucumensis (Diptera: Psychodidae) by gas chromatography of cuticular hydrocarbons.

Specimens of two species of sandfly, Psychodopygus carrerai carrerai and P. yucumensis, vectors of Leishmania braziliensis braziliensis in the subandean lowlands of Bolivia, were subjected to cuticular hydrocarbon analysis to ascertain if the technique could separate the females. A high degree of separation (87%) was obtained based on significant differences in the cuticular hydrocarbon composition of these two species. Statistical treatment of the data shows that these species, initially identified by the colour of the mesonotum, can also be distinguished by their hydrocarbons.

A new focus of cutaneous leishmaniasis due to Leishmania amazonensis in a Sub Andean region of Bolivia.

We detected a new outbreak focus with high incidence of cutaneous leishmaniasis in the Sub Andean region of La Paz. This area was never considered previously as an endemic zone of leishmaniasis. Leishmania stocks from human lesions were isolated: three stocks were explored by pulse field gradient electrophoresis, showing evidence for their affiliation to the L. mexicana complex. Eight stocks were submitted to isoenzyme electrophoresis and compared with five reference strains: L. amazonensis, L. braziliensis, L. chagasi, L. mexicana and L. pifanoi. Close genetic proximity was evidenced between newly isolated parasites and the reference stock of L. amazonensis, whereas high divergence was observed between them and either the L. pifanoi, L. mexicana, L. braziliensis and L. chagasi reference strains.

First evidence of transmission of Leishmania (Viannia) lainsoni in a Sub Andean region of Bolivia.

Using ubiquitous primers which amplify the variable parts of kDNA minicircle of all Leishmania spp, we obtained for Leishmania (viannia) lainsoni a major band of 605 bp (band 1) shared with L. V. braziliensis and a minor 524 bp band (band 2) specific of L. V. lainsoni. The specificity of the two bands was examined through Southern blot hybridization of kDNA PCR obtained from reference strains belonging to L. braziliensis, L. mexicana, L. donovani complexes with L. V. lainsoni species. Band 1 was not specific of L. V. lainsoni since it hybridized with some isolates belonging to L. braziliensis complex. In contrast, band 2 was L. V. lainsoni specific. PCR-based detection followed by hybridization with the new L. V. lainsoni probe (Band 2) and L. V. braziliensis probe (564 bp), was assayed using sample from a pool of 25 females of Lutzomiya nuneztovari anglesi, blood, skin and liver samples of 18 mammals, spinal cords of four mammals and blood and cutaneous ulcers aspirates from 95 patents from Sub Andean region of La Paz, Bolivia. We observed a ositive hybridization of four patients lesions and the pool of L. nuneztovari anglesi with the L. V. lainsoni probe. It is the first time that L. V. lainsoni is observed in a cycle of transmission in Bolivia. PCR products of three patients lesions and the pool of L. nuneztovari anglesi were also hybridized with the specific probe of L. V. braziliensis suggesting mixed infection in this focus.

[Development of a factual model for the dynamics of the transmission of infection by the human immunodeficiency virus: an example for animal epidemiology]. / Modélisation événementielle de la dynamique de la transmission de l'infection à virus de l'immunodéficience humaine: un exemple pour l'épidémiologie animale.

In order to simulate the spreading mechanism of human immunodeficiency virus (HIV), a factual approach was developed given the ease of incorporating new knowledge and taking into account the variability of a large number of sociological, biological and demographic factors, and also on account of the dynamics of the relational network of individuals. By way of example, the model was applied to data concerning homosexuals in San Francisco (United States of America) between 1980 and 1987, which enabled an evaluation to be made of the probability of HIV transmission from each partner, using two hypotheses about the evolution of contagiousness of an infected individual during the incubation period. An analysis of the sensitivity of the model revealed certain factors which had a strong influence on the growth of the epidemic. Application of this technique to the entire population of France is planned.

Blood donation and HIV infection: impact of seroconversion delay on the sensitivity of the testing procedure.

This study estimates the impact of the delay of seroconversion on the global sensitivity of the testing procedure among regular blood donors who give 80% of blood donations in France and in the USA. When applied to the 1987 French data, an estimate of 77 to 161 false negative donations, depending on the assumption concerning the mean seroconversion delay, was obtained, as compared to the 388 positive donations detected. The global sensitivity of the testing procedure ranged from 70 to 83%. When applied to the 1986-87 American data, an estimate of 192 to 432 false negative donations was obtained, as compared to the 1728 positive donations detected. The global sensitivity of the testing procedure ranged from 80 to 90%. These results emphasize the need to recruit blood donors in low risk subgroup populations and to develop more sensitive biological tests.

[Phlebotomus fauna (Diptera: Psychodidae) of 3 provinces of the northeastern region of Marañon, Peru]. / La fauna flebotómica (Diptera: Psychodidae) de tres provincias de la región nor oriental del Marañón, Perú.

Two thousand seven hundred and seventy four sand flies were captured since 1987 to 1992 in endemic areas of human bartonellosis and Peruvian Verruga (district of San José de Lourdes, province of San Ignacio - 05 degrees 03' LS, and district of Lonya Grande, province of Utcubamba - 06 degrees 05'30" LS) belonging to the Northeast region of Marañon, Peru. Thirteen species were identified, 11 belonging to the genus Lutzomyia, 1 to Brumptomyia and the other to Warileya. Lutzomyia sp, close to L. serrana and L. maranonensis n. sp., Galatti, Cáceres & Le Pont are more prevalent (89.74% of the individuals captured). Suggests working of the kind. Lutzomyia verrucarum (Townsend, 1913) is reported in Utcubamba province for the first time.

Is Lutzomyia serrana (Diptera, Psychodidae, Phlebotominae) present in Ecuador?

We describe a multivariate metric comparison of three sandfly species showing strong differences in size, which questions the geographical distribution of one of them. Two species are represented by a single population (L. robusta and L. guilvardae) and one by two populations (L. serrana). All of them belong to the series serrana (Diptera, Psychodidae, Phlebotominae). The morphometric data confirm that L. guilvardae is a distinct species. However, they suggest that L. robusta and L. serrana in Ecuador are the same taxon, and that it is distinguishable from the population of L. serrana in Bolivia. A multilocus enzyme electrophoresis analysis comparing L. serrana in Bolivia and L. robusta in Ecuador adds further evidence that these two populations are distinct species. Thus, our data seem to indicate that, in Ecuador, the population previously identified as L. serrana is actually the same species as the allopatric population previously identified as L. robusta. Accepting L. serrana in Ecuador as small-sized L. robusta, the resulting geographic distribution of this latter becomes in closer agreement with ecology and epidemiology.