Observations on the feeding habits of Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae: Phlebotominae) in Campo Grande, an endemic area of visceral leishmaniasis in Mato Grosso do Sul, Brazil

Sand flies were captured weekly with CDC light traps from December 2003 to November 2005 in three areas of Campo Grande, in the Brazilian state of Mato Grosso do Sul. These areas incorporated two patches of remnant forest and five houses. The blood meals of engorged female sand flies were identified using the avidin-biotin system of immunoenzymatic ELISA capture. Most (327/355) of the females analysed were Lutzomyia longipalpis, of which 66.4% reacted with human blood, 64.8% with that of birds and 8.9% with that of dogs. Females that had taken human blood predominated in the residential areas and two forest patches. The following combinations of blood were also detected for L. longipalpis in some of the samples analysed: bird + human (43.4%), bird + human + dog (6.1%). The combination bird + human + dog + pig was also found for Nyssomyia whitmani. Dogs and pigs appear to have little attractiveness for L. longipalpis. The results obtained demonstrate the eclecticism and high anthropophily of L. longipalpis and raise new questions with regard to the importance of dogs in VL epidemiology and the possible role of man as a source of infection for sand flies.     

Shifting from wild to domestic hosts: The effect on the transmission of Trypanosoma congolense to tsetse flies

The epidemiology and impact of animal African trypanosomosis are influenced by the transmissibility and the pathogenicity of the circulating trypanosome strains in a particular biotope. The transmissibility of 22 Trypanosoma congolense strains isolated from domestic and wild animals was evaluated in a total of 1213 flies. Multivariate mixed models were used to compare infection and maturation rates in function of trypanosome origin (domestic or sylvatic) and pathogenicity. Both trypanosome pathogenicity and origin significantly affected the ability to establish a midgut infection in tsetse flies but not the maturation rates. The interaction between pathogenicity and origin was not significant. Since being pathogenic and having a domestic origin both increased transmissibility, dominant lowly pathogenic trypanosomes from domestic environments and highly pathogenic trypanosomes from sylvatic environments presented similar levels of transmissibility: 12% and 15%, respectively.Blood meals with parasite concentration ranging from 0.05 to 50 trypanosomes/μl blood for 3 strains of T. congolense were provided to different batches of tsetse flies to evaluate the relationship between the parasite load in blood meals and the likelihood for a fly to become infected. A linear relationship between parasite load and transmissibility was observed at low parasitaemia and a plateau was observed for meals containing more than 5 trypanosomes/μl. Maximum transmission was reached with 12.5 trypanosomes/μl blood. About 50% of the flies were refractory to T. congolense, whatever their concentration in the blood meal. The results suggest that the dose–transmissibility relationship presents a similar profile for different T. congolense isolates.     

Transmissibility, by Glossina morsitans morsitans, of Trypanosoma congolense strains during the acute and chronic phases of infection

In order to verify whether chronic trypanosomal infections can affect the transmissibility of Trypanosoma congolense by tsetse flies, batches of Glossina morsitans morsitans were fed on mice infected with the same level of parasitemia (10^8.1 trypanosomes/ml of blood) of two cloned low virulent T. congolense strains during the acute and the chronic phases of infection. Results showed that the proportions of procyclic infections in flies that were fed during the acute phase (32.6% and 45.4% for isolates 1 and 2, respectively) were significantly higher (χ² = 4.7, P < 0.05 and χ² = 23.7, P < 0.0001, respectively) compared to the proportions of procyclic infections of flies fed during the chronic phase of infection (18.8% and 14.9% for isolates 1 and 2, respectively). Similarly the proportions of metacyclic infections in flies fed during the acute phase (32.6% and 45.4% for isolates 1 and 2, respectively) were significantly higher (χ² = 6.3, P < 0.05 and χ² = 23.7, P < 0.0001, respectively) compared to the proportions of metacyclic infections in flies fed during the chronic phase of infection (16.8% and 14.9% for isolates 1 and 2, respectively). No significant difference was found in the maturation rate of both strains during the acute phase compared to the chronic phase of infection (P > 0.05). The results of this study suggest that T. congolense loses part of its transmissiblity by tsetse flies during the chronic phase of infection.     

Trypanosome infections in Glossina spp. inhabiting peridomestic agroecosystems in Nsukka area, Anambra State, Nigeria

Trypanosome infections in Glossina spp. inhabiting three peridomestic agroecosystems in Nsukka area were studied by dissection from April 1984 to July 1985. Approximately 0.65% of 4620 G. tachinoides and none of 17 G. palpalis were found with maturing or mature trypanosome infections. Of these infections, 20% were due to the Trypanosoma brucei group, 40% to the T. congolense group, and 40% to a mixture of the T. brucei and T. congolense groups. Trypanosome infection rates did not differ significantly with seasons or sex of fly, but they differed significantly with location. An apparent difference was observed in the frequency with which male and female G. tachinoides were infected by the various trypanosome species. Also there was a difference in the variety of trypanosome species encountered in the three locations. In infective flies, while the salivary gland, labrum and midgut were scantily to very heavily infected, the hypopharynx was never heavily infected. Dependence of tsetse flies on domestic pigs as the major source of blood meals, commercial activities in the area, the inherently limited vectorial capacity of palpalis group tsetse, and the fact that most flies apparently obtained their first blood meal when two to four days old, were identified as some of the factors responsible for the observed infection rates. The epizootiological and epidemiological implications of these findings are discussed.     

Oviposition strategies adopted by gravid Aedes aegypti (L.) (Diptera: Culicidae) as detected by ovitraps in Trinidad, West Indies (2002-2006)

Aedes aegypti oviposition strategies were studied weekly over a period of 5 years (2002-2006) in Curepe, Trinidad using modified ovitraps. From a total of 23,293 ovitraps collected, 10,156 were collected in the months of the dry season, with 3041 positive (30%) containing 99,577 Ae. aegypti eggs. In contrast, during the wet season from 13,137 ovitraps collected, 10,652 were positive (81.9%), containing 192,209 Ae. aegypti eggs. When, the number of eggs collected and the number of positive ovitraps were divided into different egg number categories, <30, 31-60, 61-90 and >91, significantly more eggs (G = 89.6; d.f. = 4; P < 0.001) and more positive ovitraps (P < 0.001) were collected within the <30 eggs range, followed by the egg categories 31-60, 61-90 and >91 eggs. The patterns of oviposition displayed by Ae. aegypti during the early, mid and late wet and dry seasons showed a significant (F = 102.8; d.f. = 5; P < 0.002) decline in the number of eggs and oviposition occurrences from the early dry season to the late dry season among egg categories, <30 and 31-60 but no significant (F = 3.98; d.f. = 4; NS) decline in the other egg categories. In contrast, during the early, mid and late wet season, significant (F = 209.8; d.f. = 5; P < 0.02) increases were observed in the number of eggs and positive ovitraps collected among egg categories <30, 31-60, and 61-90 but with similar numbers of eggs and oviposition occurrences recorded within the >91 egg category. These results suggest that the oviposition strategies adopted depend on numerous factors including the physical state of the oviposition site, the presence of eggs from conspecific females, whether the same or different individuals and the number or clutch size already present on the oviposition site. Therefore vector control workers should employ source reduction strategies to remove the small containers which may harbour 1-30 eggs and treat the larger permanent containers like water drums which may contain >60 eggs and may be the sites of superoviposition in nature. These combined strategies can effectively control the vector populations and reduce dengue transmission in Ae. aegypti infested countries.     

Nutritional stress of adult female tsetse flies (Diptera: Glossinidae) affects the susceptibility of their offspring to trypanosomal infections

The epidemiology of tsetse-transmitted trypanosomiasis depends, among other factors, on the proportion of infected flies in a tsetse population. A wide range of intrinsic and extrinsic factors seem to determine the ability of a tsetse fly to become infected and to transmit the parasite. In this paper, we investigated the effect of nutritional stress of reproducing female Glossina morsitans morsitans on the susceptibility of their offspring to trypanosomal infections. Adult female flies that were nutritionally stressed by feeding only once a week, produced pupae with a significant lower weight and offspring with a significant lower fat content as well as a lower baseline immune peptide gene expression. Moreover, infection experiments showed that the emerging teneral flies were significantly more susceptible to a Trypanosoma congolense or Trypanosoma brucei brucei infection than flies emerging from non-starved adult females. These findings suggest that in the field, substantial nutritional stress of adult tsetse flies, as is often experienced during the hot dry season, can increase significantly the vectorial capacity of the emerging teneral flies and thus result in an increased infection rate of the tsetse population.     

In vivo experimental drug resistance study in Trypanosoma vivax isolates from tsetse infested and non-tsetse infested areas of Northwest Ethiopia

Ethiopia, particularly in the Northwest region, is affected by both tsetse fly and non-tsetse fly transmitted trypanosomosis with a significant impact on livestock productivity. The control of trypanosomosis in Ethiopia relies on either curative or prophylactic treatment of animals with diminazene aceturate (DA) or isometamidium chloride (ISM), respectively. However, since these two trypanocides have been on the market for more than 40 years, this may have resulted in drug-resistance. Therefore, in vivo drug resistance tests on two Ethiopian isolates of Trypanosoma vivax were completed, one from an area where tsetse flies are present and one from an area where tsetse flies are not present. Twenty four cattle (Bos indicus) aged between 6 and 12 months, purchased from a trypanosome-free area (Debre Brehan: Northcentral Ethiopia) and confirmed to be trypanosome-negative, were randomly assigned into four groups of six animals, which were infected with T. vivax isolated from a tsetse-infested or non-tsetse infested area, and in each case treated with curative doses of DA or ISM. Each animal were inoculated intravenously 3 × 10⁶ trypanosomes from donor animals. Parasitaemia became patent earlier in infections with non-tsetse T. vivax (∼7 days post-infection) than tsetse (∼14 days post-infection). Both groups were treated at the highest peak parasitaemia with DA or ISM and nine cattle, four with non-tsetse T. vivax (two ISM- and two DA-treated) and five with tsetse T. vivax (three ISM- and two DA-treated) showed relapses of parasitaemia. Moreover, treatment did not improve diagnostic host markers of trypanosome infections in these animals. In conclusion, in vivo drug tests indicated the presence of resistant parasites (>20% of treated animals in each group relapsed) against recommended doses of both available trypanocidal drugs.     

Phlebotomine sand fly population dynamics in a leishmaniasis endemic peri-urban area in southern Italy

A 2-year survey was carried out from May to November 2008 and 2009 to study the sand fly species composition, its seasonal phenology and density in Apulia region (southern, Italy). The study was conducted in a dog shelter located in a new residential urban district where Leishmania infantum is endemic. Sand flies were collected using sticky traps from May to November, at about 7-day intervals. Temperature and relative humidity were recorded daily. In December 2008, general environmental improvements (e.g., the ground was covered with gravel and the vegetation present inside the cages was removed to facilitate cleaning) were made in the study area. The most diffused species during the whole study period were Phlebotomus perniciosus (2008, n = 248, 49.4%; 2009, n = 254, 50.6%) followed by Phlebotomus neglectus (2008, n = 76, 39.8%; 2009, n = 115, 60.2%) and Phlebotomus papatasi (2008, n = 5, 50.0%; 2009, n = 5, 50.0%). Four specimens of Phlebotomus perfiliewi were collected only in the first year. The number of Sergentomyia minuta specimens collected increased considerably in the second (n = 548, 86.2%) in comparison to the first year (n = 88, 13.8%). The highest number of phlebotomine sand flies was collected in July and August when a mean temperature from 27.09 to 28.02 °C and mean relative humidity from 47.28 to 56.36% were recorded. The variations in phlebotomine sand fly species diversity and abundance recorded in this study were related to climatic and environmental factors. Data here presented confirm that sand flies easily adapt to the urban environments and that the may represent a public health concern for L. infantum and other pathogen transmission also in similar urban environment of southern Europe.     

Ecology of sand flies in a low-density residential rural area,with mixed forest/agricultural exploitation,in north-eastern Brazil

Cutaneous leishmaniasis caused by Leishmania braziliensis is endemic in Brazil, where Lutzomyia whitmani is the most important vector involved in the transmission to humans, particularly in the peridomestic environment. Herein, we assessed the ecology of sand flies, including Lu. whitmani, in a low-density residential rural area with mixed forest/agricultural exploitation in north-eastern Brazil, where cutaneous leishmaniasis is endemic. Particularly, we hypothesized that sand fly abundance was correlated with climatic variables. Sand fly collections were carried out monthly from August 2013 to August 2014, using seven CDC light traps, for three consecutive nights, in three kinds of environments: indoor, peridomicile and forest. Collected sand flies were identified based on morphology and females of Lu. whitmani (n = 169), Lu. amazonensis (n = 134) and Lu. complexa (n = 21) were selected and tested by PCR for Leishmania (Viannia) spp. In total, 5167 sand flies belonging to 19 species were identified, being that Lu. choti (43.2%) was the most frequent species, followed by Lu. amazonensis (16.6%), Lu. whitmani (15.8%), Lu. sordellii (10.7%) and Lu. quinquefer (5.8%), which together represented over 90% of the collected sand flies. All females tested by PCR were negative. The number of sand flies collected daily was positively correlated with temperature and negatively correlated with rainfall and relative humidity. Furthermore, there was a positive correlation between daily number of sand flies and daily average saturation deficit. This study points out that the number of sand flies captured daily is correlated to climatic variables, including saturation deficit, which may represent a useful parameter for monitoring sand fly populations in leishmaniasis-endemic areas.     

The effects of the fungus Metarhizium anisopliae var. acridum on different stages of Lutzomyia longipalpis (Diptera: Psychodidae)

The control of Visceral Leishmaniasis (VL) vector is often based on the application of chemical residual insecticide. However, this strategy has not been effective. The continuing search for an appropriate vector control may include the use of biological control. This study evaluates the effects of the fungus Metarhizium anisopliae var. acridum on Lutzomyia longipalpis. Five concentrations of the fungus were utilized, 1 × 10⁴ to 1 × 10⁸ conidia/ml, accompanied by controls. The unhatched eggs, larvae and dead adults previously exposed to fungi were sown to reisolate the fungi and analysis of parameters of growth. The fungus was subsequently identified by PCR and DNA sequencing. M. anisopliae var. acridum reduced egg hatching by 40%. The mortality of infected larvae was significant. The longevity of infected adults was lower than that of negative controls. The effects of fungal infection on the hatching of eggs laid by infected females were also significant. With respect to fungal growth parameters post-infection, only vegetative growth was not significantly higher than that of the fungi before infection. The revalidation of the identification of the reisolated fungus was confirmed post-passage only from adult insects. In terms of larvae mortality and the fecundity of infected females, the results were significant, proving that the main vector species of VL is susceptible to infection by this entomopathogenic fungus in the adult stage.     

Effect of niloticin,a protolimonoid isolated from Limonia acidissima L. (Rutaceae) on the immature stages of dengue vector Aedes aegypti L. (Diptera: Culicidae)

The aim of the present study was to evaluate the mosquitocidal activity of fractions and a compound niloticin from the hexane extract of Limonia acidissima L. leaves on eggs, larvae and pupae of Aedes aegypti L. (Diptera: Culicidae). In these bioassays, the eggs, larvae and pupae were exposed to concentrations of 2.5, 5.0, 7.5 and 10.0 ppm for fractions and 0.5, 1.0, 1.5 and 2.0 ppm for compound. After 24 h, the mortality was assessed and the LC₅₀ and LC₉₀ values were calculated for larvae and pupae. Per cent ovicidal activity was calculated for eggs after 120 h post treatment. Among the sixteen fractions screened, fraction 8 from the hexane extract of L. acidissima generated good mosquitocidal activity against Ae. aegypti. The LC₅₀ and LC₉₀ values of fraction 8 were 4.11, 8.04 ppm against Ae. aegypti larvae and 4.19, 8.10 ppm against Ae. aegypti pupae, respectively. Further, the isolated compound, niloticin recorded strong larvicidal and pupicidal activities. The 2 ppm concentration of niloticin showed 100% larvicidal and pupicidal activities in 24 h. The LC₅₀ and LC₉₀ values of niloticin on Ae. aegypti larvae were 0.44, 1.17 ppm and on pupae were 0.62, 1.45 ppm, respectively. Niloticin presented 83.2% ovicidal activity at 2 ppm concentration after 120 h post treatment and niloticin exhibited significant growth disruption and morphological deformities at sub lethal concentrations against Ae. aegypti. The structure of the isolated compound was identified on the basis of single XRD and spectral data (¹H NMR and ¹³C NMR) and compared with literature spectral data. The results indicate that niloticin could be used as a potential natural mosquitocide.     

Distribution of Lutzomyia ayacuchensis, the vector of Andean-type cutaneous leishmaniasis,at different altitudes on the Andean slope of Ecuador

Distribution of the vector species is a major risk factor for the endemicity of leishmaniasis. In the present study, the vertical distribution of Lutzomyia (Lu.) ayacuchensis, the vector of Leishmania (Leishmania) mexicana in the Ecuadorian Andes, was surveyed at different altitudes (300–2500 m above sea level) of the Andean slope. The vector species Lu. ayacuchensis was identified at an altitude of 650 m and a higher areas, and higher distribution ratio of the species was observed at higher altitudes. In addition, high ratios of L. (L.) mexicana infection were detected in higher areas, but none in lower populations of sand flies. Since an association between sand fly populations and vector competence is suggested in Lu. ayacuchensis, haplotype analysis was performed on the species from different altitudes of the study areas; however, no apparent difference was observed among populations. These results suggested that Lu. ayacuchensis in Andean slope areas of Ecuador has the potential to transmit L. (L.) mexicana and spread leishmaniasis in these areas.     

Submicroscopic infections among children with adequate clinical and parasitological response (ACPR)

The aim of the study was to re-assess the treatment outcomes of Gabonese children, treated with sulfadoxine-pyrimethamine (SP) and artesunate-mefloquine (AM) and categorized by microscopy as adequate clinical and parasitological response (ACPR), using polymerase chain reaction (PCR). Dried blood spots were collected at day 0 and day 28 and stevor gene amplification was performed to detect Plasmodium falciparum infections. Plasmodial DNA was found in 27.5% (n = 19/69) of the isolates collected at day 28; this proportion was 34.3% (n = 12/35) in the SP group and 20.6% (n = 7/34) in the AM group. This study underlines the need of an accurate and more appropriate technique such as PCR to evaluate antimalarial drug efficacy during clinical trials.     

Pigs and wild boar in Corsica harbor Echinococcus canadensis G6/7 at levels of concern for public health and local economy

Cystic echinococcosis (CE) is a parasitic zoonosis widespread in the Mediterranean area. The parasite is commonly maintained in a domestic cycle involving dogs and livestock species. As no new data have been made available for the last 15 years concerning the French Mediterranean island of Corsica, a cross-sectional survey at the slaughterhouse was conducted in 2009–2010 to describe the current presence of Echinococcus granulosus sensu lato in intermediate hosts. Only pig infections with the G6/7 genotype of Echinococcus canadensis were observed. No infection was detected in other breeding species but this should be interpreted with caution because 75% of the cows inspected during the survey were calves, and all sheep and goats were younger than two months old. In parallel four wild boars harvested during the 2010–2011 hunting season were also infected by the same genotype. These data constitute the first report of E. canadensis in France and the first molecular characterization of E. granulosus sensu lato in a wild species in France. The current prevalence observed in pigs (5.9%, n = 2527) highlights the fact that CE is still of economic concern on Corsica, an island where certain regional products are produced using pig's liver (“Figatelli”). This prevalence, and the similar one observed in wild boars (4.0%, n = 101), is a consequence of certain breeding practices and hunting practices which enable circulation of the parasite in the environment in close contact with humans.     

Effects of Ethidium (homidium bromide) on female reproductive performance of laboratory-reared tsetse flies, Glossina morsitans morsitans Westwood (Diptera: Glossinidae)

Ethidium^® (homidium bromide) is a trypanocide likely to be encountered as a violative residue in blood collected from abattoirs for feeding laboratory tsetse flies. We investigated its effect on female reproduction of Glossina morsitans morsitans. One-milligram homidium per kilogram body weight was intra-muscularly administered to four steers and blood aseptically collected from them between 15 and 30 min post-treatment, analysed for homidium levels and processed for tsetse feeding. Two hundred teneral female flies were fed on homidium-treated diet while a control group of similar number was given untreated diet and the reproductive performance of the two groups statistically compared. Ethidium^®, at 266.15 ng homidium/ml blood diet, halved A-class portion of F₁-pupae, highly reduced decline of F₁-progeny quality associated with aging parents, but had no significant effect on the pupae viability, fecundity and abortion rate of the flies. We therefore concluded that Ethidium^® has beneficial effect on laboratory tsetse attributable to clearance of unfavourable microbes mediated by the drug, and could be used as a tsetse diet additive.     

Use of insecticide-impregnated targets for the control of tsetse flies (Glossina spp.) and trypanosomiasis occurring in cattle in an area of south-west Ethiopia with a high prevalence of drug-resistant trypanosomes

In the Ghibe valley, south-west Ethiopia, a tsetse control trial using deltamethrin-impregnated targets was started in May 1990. The mean relative density of the main vector, Glossina pallidipes, fell from 2.1 flies per trap per day in the 12 months prior to introduction of tsetse control to 0.41 flies per trap per day in the 12 months after tsetse control was initiated. The annual mean prevalence of Trypanosoma congolense infections in cattle fell from 32% in the 2 years before tsetse control to 13% in the 2 years following deployment of targets. The largest reduction occurred in the first quarter of 1991 when the mean monthly trypanosome prevalence was 5%. There was also a decrease of approximately 75% in the estimated rate of relapse of trypanosome infections in cattle after treatment with diminazene aceturate. However, in June 1991, socio-political disturbances occurred in Ethiopia and were associated with substantial thefts of targets. Following these thefts, the mean relative density of G. pallidipes rose from 0.41 flies per trap per day in the period May 1990-April 1991, to 1.29 flies per trap per day in the period April 1992-March 1993. Associated with this rise, the mean trypanosome prevalence in cattle increased from 13% in the period May 1991-April 1992 to 28% in the period May 1992-April 1993. This was similar to the mean trypanosome prevalence in cattle during the pre-control period. Thus, while effective tsetse control methods can be used to reduce the transmission of trypanosomes their long-term impact is dependent on their sustainability.     

Effect of night time-intervals,height of traps and lunar phases on sand fly collection in a highly endemic area for canine leishmaniasis

The activity of phlebotomine sand flies was monitored in a sub-urban area of Sicily in order to acquire data on seasonality and to elucidate the effect of the night time-intervals, height of traps from ground and lunar phases on the abundance of the capture. The study was conducted in the farm of the University of Messina (Italy). Light traps were placed as in the following: biweekly, from dusk to dawn, and from May to November; for three consecutive nights from 18:00 to 6:00, with the net bag being changed every 2 h; for 30 days, at different heights from 18:00 to 6:00. A total of five species (i.e., Phlebotomus perniciosus, Phlebotomus neglectus, Phlebotomus sergenti, Phlebotomus perfiliewi, and Sergentomyia minuta), three of which are proven vectors of Leishmania infantum, were captured. The most abundant species was P. perniciosus (73.3%) followed by S. minuta (23.3%). The highest number of phlebotomine sand flies was collected in August and September with a peak of collection recorded in the evening (i.e., from 20:01 to 22.00). The number of phlebotomine sand flies collected at 50 cm above the ground was significantly higher (P = 0.041) than that captured at 150 cm. Results of this study shed light on the ecology of main phlebotomine species in the Mediterranean area, and on the influence of some factors, such as time and height of traps, on the light trap capture efficiency.     

Microcavia australis (Caviidae,Rodentia), a new highly competent host of Trypanosoma cruzi I in rural communities of northwestern Argentina

Rodents are well-known hosts of Trypanosoma cruzi but little is known on the role of some caviomorph rodents. We assessed the occurrence and prevalence of T. cruzi infection in Microcavia australis (“southern mountain, desert or small cavy”) and its infectiousness to the vector Triatoma infestans in four rural communities of Tafí del Valle department, northwestern Argentina. Parasite detection was performed by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR) from blood samples. A total of 51 cavies was captured in traps set up along cavy paths in peridomestic dry-shrub fences located between 25 and 85 m from the nearest domicile. We document the first record of M. australis naturally infected by T. cruzi. Cavies presented a very high prevalence of infection (46.3%; 95% confidence interval, CI = 33.0–59.6%). Only one (4%) of 23 cavies negative by xenodiagnosis was found infected by kDNA-PCR. TcI was the only discrete typing unit identified in 12 cavies with a positive xenodiagnosis. The infectiousness to T. infestans of cavies positive by xenodiagnosis or kDNA-PCR was very high (mean, 55.8%; CI = 48.4–63.1%) and exceeded 80% in 44% of the hosts. Cavies are highly-competent hosts of T. cruzi in peridomestic habitats near human dwellings in rural communities of Tucumán province in northwestern Argentina.     

Distribution of dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) mutant alleles in Plasmodium vivax isolates from Thailand

The analysis of prevalence and distribution of pvdhfr and pvdhps mutations were performed in 169 samples collected from patients with Plasmodium vivax infection who attended the malaria clinics in the provinces along the three international borders of Thailand (Thai-Myanmar, Thai-Cambodian, and Thai-Malaysian borders). SNP-haplotypes of the pvdhfr at amino acid positions 13, 33, 57, 58, 61, 117, and 173 and of the pvdhps at positions 383 and 553 were examined by nested PCR-RFLP. Significant differences in the prevalence and distribution of pvdhfr and pvdhps combination alleles were observed in P. vivax isolates collected from all the three border areas. The most prevalent combination alleles were triple mutant pvdhfr 57L/58R/117T alleles/double wild-type pvdhps alleles (n = 18), double mutant pvdhfr 58R/117N alleles/double wild-type pvdhps alleles (n = 10), and triple mutant pvdhfr 58R/61M/117N alleles/double wild-type pvdhps alleles (n = 52) or with single mutant pvdhps 383G allele (n = 28), respectively. These information on prevalence and patterns of pvdhfr and pvdhps polymorphisms obtained from the present study suggest the presence of SP pressure on P. vivax isolates in Thailand which could be linked to the introduction of malaria from neighboring countries. Results did not support the application of SP for P. vivax control program in Thailand as well as the neighboring countries.