Comparison of the Performances of Five Primer Sets for the Detection and Quantification of Plasmodium in Anopheline Vectors by Real-Time PCR

Quantitative real-time polymerase chain reaction (qrtPCR) has made a significant improvement for the detection of Plasmodium in anopheline vectors. A wide variety of primers has been used in different assays, mostly adapted from molecular diagnosis of malaria in human. However, such an adaptation can impact the sensitivity of the PCR. Therefore we compared the sensitivity of five primer sets with different molecular targets on blood stages, sporozoites and oocysts standards of Plasmodium falciparum (Pf) and P. vivax (Pv). Dilution series of standard DNA were used to discriminate between methods at low concentrations of parasite and to generate standard curves suitable for the absolute quantification of Plasmodium sporozoites. Our results showed that the best primers to detect blood stages were not necessarily the best ones to detect sporozoites. Absolute detection threshold of our qrtPCR assay varied between 3.6 and 360 Pv sporozoites and between 6 and 600 Pf sporozoites per mosquito according to the primer set used in the reaction mix. In this paper, we discuss the general performance of each primer set and highlight the need to use efficient detection methods for transmission studies.

Characterization ofTrypanosoma bruceis.l. infecting asymptomatic sleeping-sickness patients in Côte d'Ivoire: a new genetic group?

Six villagers in the Sinfra focus of sleeping sickness in Côte d'Ivoire who in 1995 were asymptomatic and refusing treatment, despite then being serologically and parasitologically positive for trypanosomes, were followed-up, while still refusing treatment, until 2002. In 2002, five of the six cases remained serologically positive but no trypanosomes could be found in any of them by use of the classical parasitological methods. A PCR-based assay, however, revealed that all six had the DNA of Trypanosoma brucei s.l. in their blood, so confirming the low sensitivity of the classical parasitological tests. The analysis of satellite, minisatellite and microsatellite markers indicated that, in 2002, all six cases were infected with a 'new' distinct genetic group of T. brucei s.l. and four were co-infected with T. b. gambiense group 1. The epidemiological consequences of such co-infections are discussed. The 'new' group of T. brucei had a molecular pattern that differed from those of the classical T. b. gambiense group 1 and the 'bouaflé' group.

Trypanosoma vivax, T. congolense "forest type" and T. simiae: prevalence in domestic animals of sleeping sickness foci of Cameroon

In order to better understand the epidemiology of Human and Animal trypanosomiasis that occur together in sleeping sickness foci, a study of prevalences of animal parasites (Trypanosoma vivax, T. congolense "forest type", and T. simiae) infections was conducted on domestic animals to complete the previous work carried on T. brucei gambiense prevalence using the same animal sample. 875 domestic animals, including 307 pigs, 264 goats, 267 sheep and 37 dogs were sampled in the sleeping sickness foci of Bipindi, Campo, Doumé and Fontem in Cameroon. The polymerase chain reaction (PCR) based method was used to identify these trypanosome species. A total of 237 (27.08%) domestic animals were infected by at least one trypanosome species. The prevalence of T. vivax, T. congolense "forest type" and T. simiae were 20.91%, 11.42% and 0.34% respectively. The prevalences of 7 vivax and T. congolense "forest type" differed significantly between the animal species and between the foci (p < 0.0001); however, these two trypanosomes were found in all animal species as well as in all the foci subjected to the study. The high prevalences of 7 vivax and T congolense "forest type" in Bipindi and Fontem-Center indicate their intense transmission in these foci.

Epidemiological study of canine trypanosomosis in an urban area of Ivory Coast

Following confirmed cases of trypanosomosis in military working dogs, a cross-sectional study was undertaken to evaluate the source of infection and determine the prevalence of canine infection with Trypanosoma congolense in the urban focus of Abidjan, Ivory Coast. Blood from 123 dogs were collected and subjected to PCR using specific primers for Trypanosoma congolense "forest type". In addition, an entomological study was conducted in an urban area near the forest surronding the military camp. The observed prevalence was 30.1% and PCR positivity to Trypanosoma congolense was not significantly associated with sex or age of animals. This study demonstrates the high contamination rate of dogs in enzootic zones, the potential risk of introduction of the disease in free animal populations and the ability of Glossina palpalis to adapt to urban areas and to transmit trypanosomosis in such areas. The factors leading to a possible emergence of canine trypanosomiasis in enzootic zones need further investigations.

Trypanosoma brucei gambiense: study of population genetic structure of Central African stocks using amplified fragment length polymorphism (AFLP)

To understand the maintenance and resurgence of historical Human African Trypanosomiasis (HAT) foci, AFLP was used to genotype 100 Central African Trypanosoma brucei s.l. stocks. This technique confirmed the high genetic stability of T. b. gambiense group 1 stocks and the micro genetic variability within Central African T. b. gambiense stocks. It revealed several T. b. gambiense genotypes and allowed the identification of minor and major genotypes in HAT foci. The coexistence of these genotypes in the same focus suggests that clustering of stocks according to HAT focus does not provide the true genetic picture of trypanosome circulating within the disease focus because the minor genotypes are generally underestimated. The presence of minor and major genotypes in HAT foci may explain the persistence and the resurgence of Central African sleeping sickness foci.

High prevalence of Trypanosoma brucei gambiense group 1 in pigs from the Fontem sleeping sickness focus in Cameroon

To understand the importance of domestic pigs in the epidemiology of human trypanosomiasis, PCR was used to identify trypanosome populations in 133 pigs from the Fontem sleeping sickness focus of Cameroon. The results from this study show that 73.7% (98/133) of pigs from the Fontem area carry at least one trypanosome species. Trypanosoma vivax, T. brucei s.l. and T. congolense forest were found in 34.6% (46/133), 40.0% (53/133) and 46.0% (61/133) of the pigs respectively. T. simiae and T. congolense savannah were not identified in these animals. The use of repeated DNA sequences detected T. b. gambiense group 1 in 14.8% (15/101) of the pigs. Such pigs can be possible reservoir hosts for T. b. gambiense group 1 and contribute to the maintenance of the disease in the area. Mixed infections were revealed in 35.3% (47/133) of the pigs. Furthermore, we observed that under natural conditions, 52.4% (11/21) of the pigs from the Fontem focus carry mixed infections with T. b. gambiense group 1. No significant difference was observed between the percentage of T. b. gambiense group 1 single and mixed infections, and between the prevalence of this trypanosome in pigs from villages with and without sleeping sickness patients.

Wild fauna as a probable animal reservoir for Trypanosoma brucei gambiense in Cameroon

In order to study the existence of a wild animal reservoir for Trypanosoma brucei gambiense in South Cameroon, blood was collected from wild animals in three human African trypanosomiasis foci and from a nonendemic control area. The 1142 wild animals sampled belonged to 36 different species pertaining to eight orders (407 primates, 347 artiodactyls, 265 rodents, 54 pangolins, 53 carnivores, 11 saurians and crocodilians, and five hyraxes). QBC and KIVI tests detected trypanosomes on 1.7% (13/762) and 18.4% (43/234) of animals examined, respectively. Using specific primers, T. brucei non-gambiense group 1 DNA was detected on 56 animals (4.9%). This infection rate was 5.3% in the endemic zone and 3.8% in the control zone. Of the 832 animals of the endemic zone, PCR revealed T. b. gambiense group 1 DNA in 18 (2.2%). These hosts included two rodents, two artiodactyls, two carnivores and two primates. T. b. gambiense group 1 was absent from animals from the nonendemic zone. A decrease in the prevalence of T. b. gambiense group 1 was observed in wild animals from the Bipindi sleeping sickness focus after a medical survey and vector control in this area. The epidemiological implications of these findings remain to be determined with further investigations.

Trypanosoma brucei s.l.: Characterisation of stocks from Central Africa by PCR analysis of mobile genetic elements

To better understand the epidemiology of sleeping sickness in the Central African sub-region, notably the heterogeneity of Human African Trypanosomiasis (HAT) foci, the mobile genetic element PCR (MGE-PCR) technique was used to genotype Trypanosoma brucei s.l. (T. brucei s.l.) isolates from this sub-region. Using a single primer REV B, which detects positional variation of the mobile genetic element RIME, via amplification of flanking regions, MGE-PCR revealed a micro genetic variability between Trypanosoma brucei gambiense (T. b. gambiense) isolates from Central Africa. The technique also revealed the presence of several T. b. gambiense genotypes and allowed the identification of minor and major ubiquitous genotypes in HAT foci. The presence of several T. b. gambiense genotypes in HAT foci may explain the persistence and the resurgence phenomena of the disease and also the epidemic and the endemic status of some Central African sleeping sickness foci. The MGE-PCR technique represents a simple, rapid, and specific method to differentiate Central African T. brucei s.l. isolates.

Infection rate of Trypanosoma brucei s.l., T. vivax, T. congolense "forest type", and T. simiae in small wild vertebrates in south Cameroon

In order to identify the infection rate of trypanosome species infecting wild animals in four localities (Bipindi, Campo, Fontem and Nditam) of southern Cameroon, 1,141 wild animals were sampled. These animals belonged to 36 species grouped in 8 orders including 407 primates, 347 artiodactyls, 264 rodents, 54 pangolins, 53 small carnivores, 11 saurians and crocodilians and 5 hyraxes. PCR using specific primers for Trypanosoma vivax, T. brucei s.l., T. congolense "forest type", and T. simiae showed that 18.7% of the animals were infected by at least one of these trypanosome species. A positive PCR result may not indicate absolutely an active infection because PCR can detect also transient infections. T. vivax (Duttonella) had the highest infection rate (9.5%) and was found in almost all the host orders studied. T. brucei s.l. mostly infected primates, rodents and some duikers (Cephalophus dorsalis and C. monticola). Trypanosomes of the subgenus Nannomonas had a lower infection rate of 5.5% (2.4% for T. simiae and 3.1% for T. congolense "forest type"). They were harboured mainly by primates, ungulates and rodents. Trypanosome infection rates were highest in Nditam (24.5%) and Bipindi (21%). T. brucei s.l. (Trypanozoon) had its maximum infection rate of 10.4% in Bipindi. The "Quantitative Buffy Coat" (QBC) and Kit for in vitro isolation techniques were used to identify 48 (6.1%) infected animals. 13 were positive using QBC, and 42 were positive by KIVI. However, PCR was negative on 16 of these infected animals, probably due to infections with other trypanosome species. This study showed that trypanosomes of the subgenera Duttonella, Nannomonas and Trypanozoon could infect small wild vertebrates as has been shown for large ungulates and carnivores. The presence of T. brucei s.l. in a large range of wild animals strengthens the hypothesis of the existence of a wild animal reservoir of T. b. gambiense in Cameroon.

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method is described. Domestic and wild animal blood samples were collected to extract the corresponding reference DNAs. In Campo (south Cameroon), tsetse flies (mainly Glossina palpalis palpalis) were trapped and 41 bloodmeals were collected. All reference DNAs and 37 bloodmeal DNAs (90.7%) were successfully amplified and hybridised. Twelve bloodmeals (32.4%) were of human origin, 13 (35.4%) were from Sitatunga (Tragelaphus spekei) (an antelope) while 12 (32.4%) were not identified using our set of reference DNAs. The results confirmed the occurrence of frequent contacts between wild animals and this population of tsetse flies.

An isoenzyme survey ofTrypanosoma bruceis.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 gambiensegroup I and 3T. brucei‘non-gambiense’ stocks.T. b. gambiensegroup 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 inT. 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 forT. b. gambiensegroup I in Cameroon.

Identification of trypanosomes in wild animals from southern Cameroon using the polymerase chain reaction (PCR)

One possible explanation of the maintenance of many historical foci of sleeping sickness in Central Africa could be the existence of a wild animal reservoir. In this study, PCR was used to detect the different trypanosome species present in wild animal captured by hunters in the southern forest belt of Cameroon (Bipindi). Trypanosomes were also detected by a parasitological method (Quantitative buffy coat: QBC). Parasite could not be isolated in culture medium (Kit for in vitro isolation: KIVI). Specific primers of T. brucei s.l., T. congolense forest type, T. congolense savannah type, T. vivax, T. simiae and T. b. gambiense group 1 were used to identify parasites in the blood of 164 animals belonging to 24 different species including ungulates, rodents, pangolins, carnivores, reptiles and primates. Of the 24 studied species, eight were carrying T. b. gambiense group 1. Those parasites pathogenic to man were found in monkeys (Cercocebus torquatus and Cercopithecus nictitans), in ungulates (Cephalophus dorsalis and C. monticola), in carnivores (Nandinia binotata and Genetta servalina) and in rodents (Cricetomys gambianus and Atherurus africanus). 13 species (54%) were carrying T. brucei s.l. identified as non-gambiense group 1.

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.

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%).

[The focus of human trypanosomiasis in Campo (Cameroon). History and endemic situation in 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.

Detection and identification of trypanosomes by polymerase chain reaction in wild tsetse flies in Cameroon

The prevalence of various species and subgroups of trypanosomes in infected flies from three sleeping sickness foci in Cameroon was determined by the use of polymerase chain reaction (PCR). The predominant tsetse species found were Glossina palpalis palpalis. Microscopical examination of 943 non-teneral tsetse flies revealed an average infection rate of 10.4%. A total of 90 flies were analyzed for trypanosome identification with primer sets specific for Trypanosoma (Trypanozoon) brucei s.l., T. (Duttonella) vitax, T. (Nannomonas) simiae, and forest type T. (Nannomonas) congolense. PCR succeeded in identifying 52 of the 90 infected flies. Other primers were also tested on microscope positive/PCR-negative infections, and trypanosome subgroups were detected (Kilifi type and savannah type T. congolense). PCR amplification allowed identification of immature infections and revealed mixed-infections. The PCR technique failed to identify 42.2% (38/90) of the parasitologically positive flies and the reasons for this failure are discussed.

Polymorphic microsatellites in Simulium damnosum s.l. and their use for differentiating two savannah populations: implications for epidemiological studies

In West Africa, Onchocerca volvulus, the cause of human onchocerciasis, is transmitted by sibling species of the Simulium damnosum complex. Little is known about blackfly intraspecific variability and its consequences on vectorial capacity. This study reports the use of microsatellite markers for differentiating populations of S. damnosum s.l. Five microsatellite loci were characterized and used to analyze individuals from two savannah populations in Mali, 120 km apart. Four loci were highly polymorphic, having 8-12 alleles per locus and gene diversities ranging from 77.9 to 88.2%. A significant heterozygote deficiency was observed in the two populations. This may arise from inbreeding, population structure (the Walhund effect), or the presence of null alleles. To test this last hypothesis, new primers were designed for two loci and used to analyze homozygous individuals. After correcting for null alleles, heterozygote deficit persisted. Population subdivision in the two foci remains the most likely explanation. Our results indicate that microsatellite markers could differentiate fly populations, making them valuable tools for the study of population genetic structure.

Genomic fingerprinting of Onchocerca species using random amplified polymorphic DNA

A method based on amplification of genomic DNA by decamer primers of random nucleotide sequence was used to obtain DNA fingerprints from different species of the genus Onchocerca. Each of the 20 primers tested allowed a clear distinction between the different species of the genus on an agarose gel. The technique offers the potential to construct species or strain specific probes and oligonucleotides PCR primers from the species specific fragments. A combination of these primers or others could be useful as population markers.

Restriction map of the Casphalia extranea densovirus genome

A physical map of the Casphalia extranea densovirus genome (CeDNV) was constructed. The size of the intact viral genome was estimated to be 4.9 kilobases or 1.6 MDa (single strand). The double-stranded CeDNV genomic DNA was cleaved with 26 restriction endonucleases and 20 restriction sites were mapped on the genome. The CeDNV DNA restriction map was compared to those of other densoviruses. Southern blotting hybridization experiments failed to reveal any homology between the genomes of CeDNV and Junoniacoenia densovirus (JcDNV).

Arteriovenous malformations of the brain in children

A survey of 23 children treated for arteriovenous malformations of the brain is presented. Venous angiomas and aneurysms of the vein of Galen were excluded. Spontaneous hemorrhage was the first symptom in 83%. Angiographically occult arteriovenous malformations were found in 22% of cases. Contrast-enhanced CT failed to opacify abnormal vessels in most of these occult lesions. Fourteen patients underwent complete excision of their malformation with only 1 death (7.1% surgical mortality). Overall mortality for the group was 21.7%. Outcome was related to treatment modality and clinical condition on presentation. Four of 8 patients presenting in deep coma died, but 3 are normal and one slightly disabled. A spontaneous cerebral hemorrhage in a child is probably due to a vascular malformation, even when angiography and enhanced CT are negative. Optimal management consists of complete removal of the malformation; residual lesions tend to rebleed with fatal outcome. With aggressive treatment, complete recovery is possible even for children who present in coma.

Temporal lobe gangliogliomas in children

The ganglioglioma, a mixed tumor with neuronal and glial elements, occurs occasionally in children and young adults. Its incidence, clinical presentation, radiological features, and natural history have not been clearly defined. A review of 111 primary brain tumors treated at our institution shows that 9.0% were gangliogliomas. The temporal lobe was the most common site involved. All patients presented with seizures but were neurologically intact. The CT scan showed a partially calcified mass, frequently isodense or nearly so, with minimal enhancement. Complete removal produced dramatic improvement in seizure control. Radiotherapy and/or chemotherapy are reserved for tumors showing malignant changes in the astrocytic component. Patients with chronic epilepsy, or whose seizures escape control despite anticonvulsants, should be examined with this tumor in mind. Following removal of these low-grade temporal lobe tumors, fewer seizures are seen, and the long-term prognosis is very good.

Neonatal intracranial teratoma. Case report

The authors report the successful total excision of an intracranial teratoma in a neonate. The pathology of this rare tumor and its prognosis in relation to the maturity of individual cell lines is discussed. A review of the previous operation experience in the neonatal age group shows that radical surgical excision of the tumor has seldom been attempted. There are no reported survivors with normal neurological development. The clinical presentation, preoperative evaluation, and operative management are discussed. Emphasis is laid on intensive supportive care in the perioperative period. The difficulty in predicting a benign or malignant course in these tumors justifies extreme caution in making a prognosis and demands careful follow-up supervision. Reoperation is indicated for recurrent benign tumors; malignant germ-cell tumors may respond to combined irradiation and chemotherapy.