Spontaneous cure of domestic pigs experimentally infected by Trypanosoma brucei gambiense. Implications for the control of sleeping sickness.

The existence of a pig reservoir for human African trypanosomosis (HAT) due to Trypanosoma brucei gambiense complicates the fight against this disease. This study, reports results obtained from pigs, which were inoculated with the blood of a person, suffering from HAT in Cameroon. The pigs were reared and kept in the shelter from all contact with Glossina, and monitored for 188 days. The seroconversion was checked by agglutination assays for trypanosomosis (CATT 1.3 and LATEX/T.b.gambiense). The parasitemia was measured by quantitative buffy coat method (QBC) and by polymerase chain reaction method (PCR). In addition, growth was recorded as well as blood counting and blood formulas. The results showed that the pigs were trypanotolerant and cure themselves in less than 6 months. It is concluded that sterilisation of this reservoir could be achieved by tsetse-control measures in 1 year. It confirms the strategy to complement screening and treatment of HAT with tsetse fly control measures.

Diagnosis of human trypanosomiasis, due to Trypanosoma brucei gambiense in central Africa, by the polymerase chain reaction.

During a mass screening of sleeping sickness conducted in 1998 and 1999, and involving 27,932 persons in Cameroon and the Central African Republic, we tested the polymerase chain reaction (PCR) on whole blood for the diagnosis of human African trypanosomiasis due to Trypanosoma brucei gambiense. The 1858 samples obtained were from 4 groups: 155 infected patients, 1432 serological suspects detected by the card agglutination test for trypanosomiasis (CATT), 222 negative controls living in the prospected area (negative with the CATT and parasitological methods), and 49 negative controls (CATT and parasitological methods) and unexposed to the disease (Europeans). The technique of DNA extraction used made it possible to preserve the blood samples in the field. The primers used were specific for T. brucei s.l. Only 1 patient was PCR negative, and 3 of the negative controls, exposed to the disease, were PCR positive. Among the 1432 serological suspects, only 50 were PCR positive. During the 6-month follow-up after the surveys, the 3 negative controls, who were initially positive by PCR, were found to be negative. These initial positive PCR results are unlikely to have been due to a cross-reaction with T. brucei brucei, which is non-pathogenic for man, but are more likely to have resulted from a mislabelling of sample tubes. All control individuals, exposed or not to the disease, were negative by PCR. The PCR-negative patient was possibly a registration error. Among 50 PCR positive serological suspects, 39 of them were re-examined. Five were found to be positive by the kit for in-vitro isolation of trypanosomes, representing an increase in patients of almost 13%. At the end of the study, 160 patients were diagnosed, and the PCR was positive for 159 of them (99.4%). Moreover, the PCR made it possible to reduce the number of suspects to be re-examined (50 instead of 1432; a reduction of 96.5%).

Evaluation of LATEX/T.b.gambiense for mass screening of Trypanosoma brucei gambiense sleeping sickness in Central Africa.

We compared the Card Agglutination Test for Trypanosomiasis (CATT), which consists of lyophilized bloodstream form trypomastigotes of Trypanosoma brucei gambiense (T.b.g.) variable antigen type LiTat 1.3, with LATEX/T.b.g., which consists of a lyophilized suspension of latex particles coated with variable surface glycoproteins of T.b.g. variable antigen types LiTat 1.3, 1.5 and 1.6. This study was carried out during two mass screening surveys in 1998 in Campo, a sleeping sickness focus in Cameroon, with a low prevalence (0.3%) and in 1999 in Batangafo which belongs to the Central African focus of Ouham which has a higher prevalence (3%). In Campo, we compared the CATT performed on whole blood with the LATEX/T.b.g. on diluted blood. In Batangafo, both tests were performed on diluted blood. In all circumstances, the specificity of the LATEX/T.b.g. was higher than of CATT. The use of LATEX/T.b.g. on diluted blood instead of CATT results in an important decrease of workload and as a consequence, of costs related to parasitological examinations. In the case of Campo the workload was up to 12 times less than when using CATT 1.3 on whole blood and the cost divided by 3. In Batangafo the workload was decreased by nearly 20% with the LATEX/T.b.g. Finally, it should be noted that in Batangafo, one of the parasitologically confirmed sleeping sickness patients was negative in CATT and positive in LATEX/T.b.g. and that the reading of the test result in LATEX/T.b.g. is easier than in CATT.

Characterization of Trypanosoma brucei s.l. subspecies by isoenzymes in domestic pigs from the Fontem sleeping sickness focus of Cameroon.

Though it has been established that domestic animals (especially the pig) are potential reservoir hosts for Trypanosoma brucei gambiense in West Africa, there is little data to this effect concerning Central Africa. Instead, some previous authors report the absence of Trypanozoon type trypanosomes in domestic animals in Cameroon. Thirty-two domestic pigs were sampled by KIVI (kit for in vitro isolation) of trypanosomes in the northern region (Bechati) of the Fontem sleeping sickness focus of Cameroon. Twenty-one of these were found positive, from 15 of which 17 isolates were successfully obtained. Isoenzyme characterization revealed that isolates from 4 of the 15 pigs belonged to zymodemes associated with T. brucei gambiense group 1. The prevalence of this disease in the local human population is, however, very low. It is evident from this study that the domestic pig may be a potential reservoir host for T. brucei gambiense in the Fontem focus. There is, however, need for an extensive study on domestic animals in Cameroon and other neighbouring countries for a better comprehension of the epidemiology of sleeping sickness within the Central African region.

Spatial and temporal patterns of human African trypanosomosis (HAT) transmission risk in the Bipindi focus, in the forest zone of southern Cameroon.

Vector control is an effective and cost-efficient way to disrupt the transmission of human African trypanosomosis (HAT); it has nonetheless been little used to date in the disease's foci. With the aim to target trapping more precisely and to develop an optimized vector control system, a transmission risk index was used in the HAT focus of Bipindi, in the forest zone of southern Cameroon. The authors used a simplified version of the index originally developed by Laveissière et al. in 1994. The calculation of this new index only requires knowledge of the proportion of teneral flies and the proportion of flies with human blood meals in samples caught in different biotopes. This makes it possible to identify the biotopes displaying permanent risk, such as riverbanks, as well as biotopes displaying seasonal risk, such as marshy hollows and encampmemts. In the villages, the domestic pig, with 49% of the identified blood meals, is the favorite host of the tsetse flies during the short rainy season. The proportion of blood meals taken on human beings does not significantly increase when domestic pigs are absent. Game animals, contributing to 46% and 64% of the blood meals during the short rainy season and the long dry season, respectively, are also favored as feeding hosts in this particular HAT focus.

Population structure of Trypanosoma brucei S. L. in Cote d'Ivoire assayed by multilocus enzyme electrophoresis: epidemiological and taxonomical considerations.

Fifty-two Trypanosoma brucei stocks isolated in Côte d'Ivoire from sympatric locations were analyzed by cellulose acetate electrophoresis of isoenzymes. Of 13 genetic loci surveyed, 5 appeared as variable, which made it possible to delimit 12 different zymodemes. The most abundant zymodeme involved stocks isolated from both humans and pigs, which is consistent with the hypothesis that pig is a reservoir of human African trypanosomiasis in Côte d'Ivoire, as already proposed by other authors. Population genetic analysis of the isozyme data indicated a strong linkage disequilibrium, which suggests that genetic recombination is severely restricted in this sample and favors the hypothesis that the trypanosome populations surveyed are basically clonal. Nevertheless, additional studies are required to better estimate the long-term stability of these clones and the possible interference of gene exchange at an evolutionary scale. The results corroborate the hypothesis that a majority of human T. brucei stocks from West Africa correspond to a fairly homogeneous cluster of genotypes (T. brucei gambiense 'Group I', Gibson, 1986).

Improvement of blood and fly gut processing for PCR diagnosis of trypanosomosis.

We have adapted a simple and efficient technique to detect trypanosomes in human blood, without DNA purification, and increased the sensitivity threshold to 1 parasite in 1 ml. We have then applied it for detection of parasites in midguts of tsetse flies, negative by microscopy. This technique has been developed for field conditions and could greatly facilitate epidemiological studies.

[Where is the focus of human trypanosomiasis in Mossaka (Congo)]. / Où en est le foyer de trypanosomiase humaine de Mossaka (Congo)?

The Mossaka focus of sleeping sickness (on the Sangha, Cuvette area, in Congo) has been progressing dramatically for last years. In 1989, after a prospection we had accomplished in the focus, we had insisted on the priority to limit an extension of the disease. Since then the situation get worse, regarding to the number of patients detected (74 in 1987, 171 in 1989, 200 in 1991) and the concerned population. The number of villages where we detected patients is raised from 3 in 1987 to 12 in 1989 and 17 in 1991. If measures are not taken quickly, we can await a dramatic extension of lower Sangha focus.

[Invasions of Paederus sabaeus (Coleoptera Staphylinidae) in central Africa. 2. Clinical and therapeutic aspects in Brazzaville]. / Invasions de Paederus sabaeus (Coléoptère Staphylinidae) en Afrique centrale. 2. Aspects cliniques et thérapeutiques à Brazzaville.

During the month of May 1993, at the end of the rainy season, an outbreak of dermatitis occurred in Brazzaville (Congo). It was caused by Paederus sabaeus, a Staphylinid beetle which invaded the town during three weeks. The patients recovered spontaneously or after topical application of creams. No eye affection was recorded.

[Invasions of Paederus sabaeus (Coleoptera Staphylinidae) in central Africa. 1. Entomological and epidemiological aspects]. / Invasions de Paederus sabaeus (Coléoptère Staphylinidae) en Afrique centrale. 1. Aspects entomologiques et épidémiologiques.

In May 1993, at the end of the rainy season, outbreaks of Paederus sabaeus (Coleoptera, Staphylinidae) were recorded in Brazzaville (Congo), Kinshasa (Zaire), Franceville and Libreville (Gabon) and even in Bangui (CAR) at the North of the equator. A short review of previous outbreaks in Africa and on vesicant substances is given by the authors. These beetles are attracted to neon lights and they rest on the walls or on the skin of the occupants. When the insects are crushed on the bare skin their haemolymph liberate pederine and related vesicant components which provocate dermatitis. The insects disappeared spontaneously after three to four weeks.

[Current recrudescence of human trypanosomiasis in the Sangha focus (basin) in the Congo]. / Recrudescence actuelle de la trypanosomiase humaine dans le foyer de la Sangha (cuvette) au Congo.

In the Congo the Sangha focus of sleeping sickness caused more than 500,000 deaths in the early 20th century. Despite many years of quiescence many new cases have been detected since the early eighties. In 1987 an investigation found 43 infected patients within 5 villages (during the same year, 74 cases were detected from both investigation and passive detection). In December 1989 our further investigation found 96 new documented cases (115 for the whole year). The prevalence is increasing and the proportion of early stage in comparison with later stage is decreasing. The age diagram resembles that of the early 20th century. Despite the fact that the survey in 1989, extracted twice as many patients as in 1987 passive detection detected 99 infected patients in 1990, three times as many cases as in 1988, and places the "Sangha focus" in IId place in the Congo, after the "Bouenza focus". As only river transport is available to have access to that focus, the Congo will be faced with considerable difficulties in the future.

[The focus of human trypanosomiasis in Campo (Cameroon). History and endemic situation in 1998]. / Le foyer de trypanosomose humaine de Campo (Cameroun). Historique et situation de l'endémie en 1998.

For the first time in the last thirteen years, the human sleeping sickness focus at Campo, spanning the Cameroon-Equatorial Guinea border areas, has been prospected. The screening was carried out simultaneously on both sides of the border. This focus has been known since the beginning of the century but, contrary to what took place in other well-known foci in bordering countries south of Cameroon, either in the 1920s or the 1980s--there has never been an epidemic outbreak in that area. Such an epidemiological situation makes this focus particularly interesting. Though still active, trypanosomiasis is not very manifest. According to passive screening carried out in recent years, the estimated prevalence ranges between 0.2 and 0.5%. For this screening, 5,255 persons were examined on the Cameroonian side of the focus (90.6% of the census population). The serological screenings were carried out with the CATT 1.3, which is the CATT generally used in screening, and with the latex CATT which associates LiTat 1.3, 1.5 and 1.6. The search for trypanosomes was made by testing the lymph nod juice in presence of adenopathy and in the blood by Quantitative Buffy Coat (QBC), the mini anion exchange centrifugation (mAEC), as well as the in vitro culture using the kit for in vitro isolation of trypanosomes (KIVI) for individuals suspected to be serologically positive. 16 patients were identified in Cameroon but none in Equatorial Guinea. The results show that the Campo focus is active only on the Cameroonian side, centred on the village of Ipono with a limited prevalence (0.3%). The persisting epidemic is most likely to be associated with the presence of pigs carrying the Trypanosoma brucei gambiense which was identified during the study in Ipono. The strain that we isolated was studied by isoenzyme electrophoresis on cellulose acetate. Its zymodeme is the same as that of the human strain isolated in Campo. With the collected epidemiological data, a concerted medical and entomological action could be planned within the limits of the village of Ipono to eradicate the disease. This action may be organised by the existing local health structures. During this study, the latex CATT proved to be more cost-effective than the CATT 1.3 since a similar result was reached requiring eight times less work at a lower cost. This remains to be confirmed in a hyperendemic focus.

[Bilharziasis and human immunodeficiency virus infection in Congo]. / Bilharziose et infection par le virus de l'immunodeficience humaine au Congo.

To assess the relationship between schistosomiasis and human immunodeficiency virus (HIV) infection, a cross-sectional study of HIV seroprevalence was carried out in 1992 in a village in the Bouenza region of the Congo where there is a high incidence of urinary schistosomiasis. No correlation was found between eggs in urine and positive serology for HIV in the 895 adults examined nor between positive schistosome serology and positive HIV serology. The incidence of frank schistosome infection (eggs in urine and positive blood tests) was significantly lower in patients with positive HIV serology (3.5%) than in patients with negative HIV serology (6.7%). Similarly the mean number of eggs in urine was significantly lower in patients with positive HIV serology (3.6 eggs per ml) than in patients with negative HIV serology (26.6 eggs per ml) (p < 0.01). These observations suggest that HIV infection limits schistosome development and decreases antibody production. Further study will be needed to confirm these findings.

Human African trypanosomiasis in Angola: clinical observations, treatment, and use of PCR for stage determination of early stage of the disease.

Biological and clinical observations are described for 224 patients infected by human African trypanosomiasis (HAT) in Angola in 2007 and 2008. Seven patients were initially classified in stage 1 (S1), 17 intermediate stage (IS) (WBC <20 lymphocytes/µl with absence of trypanosomes in cerebrospinal fluid (CSF) and no neurological signs), and 200 in stage 2 (S2). Out of 224 patients, 165 (73.6%) presented one or more neurological signs. During treatment with eflornithine, six deaths of S2 patients occurred, five of which were because of an encephalopathy syndrome. Nine patients were diagnosed with a relapse or suspected treatment failure during the follow-up: eight patients after treatment with eflornithine (relapse rate 4.1%) and one patient after pentamidine (6.6%). The contribution of PCR for stage determination evaluated for S1 and IS confirms the difficulty of stage determination, as one S1 patient and two IS patients were carriers of trypanosomes detected a posteriori by PCR in CSF but were treated with pentamidine while follow-up did not confirm treatment efficacy. Since 2001 in Angola, either by passive or active mode detection, approximately 80% of the new cases every year were in S2, whereas the annual number of cases has regressed, probably because the transmission of HAT is decreasing. However, stage determination and treatment remain two major issues for the chronic form of sleeping sickness.

[Influence of mosquito nets impregnated with deltamethrin on the aggressivity cycle of Anopheles gambiae in Djoumouna, Congo]. / Influence des moustiquaires imprégnées de deltaméthrine sur le cycle d'agressivité d'Anopheles gambiae à Djoumouna, Congo.

Several studies recently done in Africa south of the Sahara have clearly demonstrated that pyrethroid impregnated bednets should actually reduce malaria inoculation rate due to Anopheles gambiae and therefore high Plasmodium falciparum parasitaemia and malaria morbidity, even mortality. Nevertheless some concerns were recently raised on an eventual shift in the usual behavior of this species induced by the presence inside the house of bednets treated with pyrethroid insecticide known to have a deterrent or excito-repellent effect, and which could therefore lead to a biting behavior earlier than usual. The current limited study, done in Djoumouna, a place well known for the very high density of An. gambiae, has shown that the temporary presence inside a house of a bednet impregnated with deltamethrin (12.5 or 25 ma a.i./m2) has not induced any shift in the biting cycle of this species, but it actually reduced by some 50% its biting rate noticed on human beings. It is worth underlining that all sporozoite infected specimens were actually caught after midnight. This biting behavior of An. gambiae could explain why impregnated bednets are so efficient in reducing man-vector contact and malaria transmission.

[Attempt at defining dermatological criteria for surveys of African onchoceriasis based on observations made in 3 Mali villages]. / Essai de définitions des critères dermatologiques pour les enquêtes sur l'onchocercose africaine d'après les constatations faites dans trois villages maliens.

The study done by the authors at the Marchoux Institute of Bamako and in 3 Malian villages of the Koutiala area (two of hyperendemic and one of hypoendemic onchocerciasis) emphasized the interest which can be represented in the epidemiologic investigations on the onchocerciasis: the tibial vitiligo and the cutaneous atrophy. The dyschromia of more suggestive appreciation is less usable. Prurigo, lichenification, hypochromia and hyperchromia have less interest in these investigations because of more other causes which can be attributed to them.

[Paraclinical study of onchocercosis in a leprous and non-leprous population]. / Etude paraclinique de l'onchocercose en population lépreuse et non lépreuse.

In a survey dealing with the frequency of onchocerciasis in leprous environments in the Marchoux Institute in Bamako (Mali) evidence is given that 43% of the leprous persons hospitalized there were touched in addition by onchocerciasis whereas, only 14% of the consultants in dermatology have proved to be also onchocercian. This last frequency is consistent with the overall estimation usually recognized for Mali. No difference was shown between leprous and non-leprous persons for snip. In contrast, 33% of microfilariae bearing leprousians showed no positive reaction to diethylcarbamazine whereas no more than 5% of non-leprous persons displayed similar negative response. Similarly leprousian blood yielded most often the microfilariae of Onchocerca volvulus. Surprisingly, hypereosinophilia has proved to be normal or null in 37% of microfilariae bearing leprosians. Though aware of the occurrence of numerous real or possible biases in such an approach the authors wonder what meaning such a difference between leprous populations and non-leprous ones in Mali can have. If a relation is definitely borne out in the future between both pathologies, they further wonder whether leprosy is the bed of onchocerciasis or vice versa.

An isoenzyme survey of Trypanosoma brucei s.l. from the Central African subregion: population structure, taxonomic and epidemiological considerations.

In order to improve our knowledge about the taxonomic status and the population structure of the causative agent of Human African Trypanosomiasis in the Central African subregion, 169 newly isolated stocks, of which 16 came from pigs, and 5 reference stocks, were characterized by multilocus enzyme electrophoresis, for 17 genetic loci. We identified 22 different isoenzyme profiles or zymodemes, many of which showed limited differences between them. These zymodemes were equated to multilocus genotypes. UPGMA dendrograms revealed one main group: Trypanosoma brucei gambiense group I and 3 T. brucei 'non-gambiense' stocks. T. b. gambiense group I zymodemes were very homogenous, grouping all the human stocks and 31% of the pig stocks. Two main zymodemes (Z1 and Z3) grouping 74% of the stocks were found in different remote countries. The genetic distances were relatively high in T. brucei 'non-gambiense' zymodemes, regrouping 69% of pig stocks. The analysis of linkage disequilibrium was in favour of a predominantly clonal population structure. This was supported by the ubiquitous occurrence of the main zymodemes, suggesting genetic stability in time and space of this parasite's natural clones. However, in some cases an epidemic population structure could not be ruled out. Our study also suggested that the domestic pig was a probable reservoir host for T. b. gambiense group I in Cameroon.