Parasites & Vectors - Latest Articles

Synthetic sex pheromone attracts the leishmaniasis vector Lutzomyia longipalpis to experimental chicken sheds treated with insecticide

Daniel Bray — 2010-03-11T00:00:00Z

Background: Current strategies for controlling American visceral leishmaniasis (AVL) have been unable to prevent the spread of the disease across Brazil. With no effective vaccine and culling of infected dogs an unpopular and unsuccessful alternative, new tools are urgently needed to manage populations of the sand fly vector, Lutzomyia longipalpis Lutz and Neiva (Diptera: Psychodidae). Here, we test two potential strategies for improving L. longipalpis control using the synthetic sand fly pheromone (+/-)-9-methylgermacrene-B: the first in conjunction with spraying of animal houses with insecticide, the second using coloured sticky traps. Results: Addition of synthetic pheromone resulted in greater numbers of male and female sand flies being caught and killed at experimental chicken sheds sprayed with insecticide, compared to pheromone-less controls. Furthermore, a ten-fold increase in the amount of sex pheromone released from test sheds increased the number of females attracted and subsequently killed. Treating sheds with insecticide alone resulted in a significant decrease in numbers of males attracted to sheds (compared to pre-spraying levels), and a near significant decrease in numbers of females. However, this effect was reversed through addition of synthetic pheromone at the time of insecticide spraying, leading to an increase in number of flies attracted post-treatment.In field trials of commercially available different coloured sticky traps, yellow traps caught more males than blue traps when placed in chicken sheds. In addition, yellow traps fitted with 10 pheromone lures caught significantly more males than pheromone-less controls. However, while female sand flies showed a preference for both blue and yellow pheromone traps sticky traps over white traps in the laboratory, neither colour caught significant numbers of females in chicken sheds, either with or without pheromone. Conclusions: We conclude that synthetic pheromone could currently be most effectively deployed for sand fly control through combination with existing insecticide spraying regimes. Development of a standalone pheromone trap remains a possibility, but such devices may require an additional attractive host odour component to be fully effective.

The development of drugs for treatment of sleeping sickness: a historical review

Dietmar Steverding — 2010-03-10T00:00:00Z

Only four drugs are available for the chemotherapy of human African trypanosomiasis or sleeping sickness; suramin, pentamidine, melarsoprol and eflornithine. The history of the development of these drugs is well known and documented. Suramin, pentamidine and melarsoprol were developed in the first half of the last century by the then recently established methods of medicinal chemistry. Eflornithine, originally developed in the 1970s as an anti-cancer drug, became a treatment of sleeping sickness largely by accident. This review summarises the developmental processes which led to these chemotherapies from the discovery of the first bioactive lead compounds to the identification of the final drugs.

Scientometric analysis of the world-wide research efforts concerning Leishmaniasis

K Al-Mutawakel — 2010-03-04T00:00:00Z

Background: Leishmaniasis is a chronic disease that is found in various countries of the world. The aim of the current study was to investigate the impact of leishmaniasis on the world's research output. The present study assessed benchmarking of research output for the period between 1957 and 2006. Using large database analyses, research in the field of leishmaniasis was evaluated. Furthermore, cooperation between different countries was identified. Results: The number of publications increased with time. Most publications came from Western countries such as the US, UK or Germany. Interestingly, countries like Brazil and India had a high research output. We found a substantial amount of cooperation between countries. Conclusion: Although leishmaniasis is of limited geographic distribution it attracts a wide research interest. The central hub of research cooperation is the USA.

Simplified molecular detection of Leishmania parasites in various clinical samples from patients with leishmaniasis

Claire Mugasa — 2010-03-02T00:00:00Z

Background: Molecular methods to detect Leishmania parasites are considered specific and sensitive, but often not applied in endemic areas of developing countries due to technical complexity. In the present study isothermal, nucleic acid sequence based amplification (NASBA) was coupled to oligochromatography (OC) to develop a simplified detection method for the diagnosis of leishmaniasis. NASBA-OC, detecting Leishmania RNA, was evaluated using clinical samples from visceral leishmaniasis patients from East Africa (n=30) and cutaneous leishmaniasis from South America (n=70) and appropriate control samples. Results: Analytical sensitivity was 10 parasites/ml of spiked blood, and 1 parasite/ml of culture. Diagnostic sensitivity of NASBA-OC was 93.3% (95% CI: 76.5%-98.8%) and specificity was 100% (95% CI: 91.1%-100%) on blood samples, while sensitivity and specificity on skin biopsy samples was 98.6% (95% CI: 91.2%-99.9%) and 100% (95% CI: 46.3%-100%), respectively. Conclusion: The NASBA-OC format brings implementation of molecular diagnosis of leishmaniasis in resource poor countries one step closer.

Attracting, trapping and killing disease-transmitting mosquitoes using odor-baited stations -The Ifakara Odor-Baited Stations

Fredros Okumu — 2010-03-01T00:00:00Z

Background: To accelerate efforts towards control and possibly elimination of mosquito-borne diseases such as malaria and lymphatic filariasis, optimally located outdoor interventions could be used to complement existing intradomicilliary vector control methods such as house spraying with insecticides and insecticidal bednets. Methods: We describe a new odor-baited station for trapping, contaminating and killing disease-transmitting mosquitoes. This device, named the 'Ifakara Odor-baited Station' (Ifakara OBS), is a 4m3 hut-shaped canvas box with seven openings, two of which may be fitted with interception traps to catch exiting mosquitoes. It is baited with synthetic human odors and may be augmented with contaminants including toxic insecticides or biological agents. Results: In field trials where panels of fabric were soaked in 1% pirimiphos-methyl solution and suspended inside the Ifakara OBS, at least 73.6% of Anopheles arabiensis, 78.7% of Culex and 60% of Mansonia mosquitoes sampled while exiting the OBS, died within 24 hours. When used simply as a trap and evaluated against two existing outdoor traps, Ifakara Tent trap and Mosquito Magnet-X(R), the OBS proved more efficacious than the Ifakara Tent trap in catching all mosquito species found (P<0.001). Compared to the Mosquito Magnet-X(R), it was equally efficacious in catching An. arabiensis (P=0.969), but was less efficacious against Culex (P<0.001) or Mansonia species (P<0.001). Conclusion: The Ifakara OBS is efficacious against disease-carrying mosquitoes including the malaria vector, An. arabiensis and Culicine vectors of filarial worms and arboviruses. It can be used simultaneously as a trap and as a contamination or killing station, meaning most mosquitoes which escape trapping would leave when already contaminated and die shortly afterwards. This technique has potential to complement current vector control methods, by targeting mosquitoes in places other than human dwellings, but its effectiveness in the field will require cheap, long-lasting and easy-to-use mosquito lures.

Capillariaisis (Trichurida, Trichinellidae, Capillaria hepatica) in the Brazilian Amazon: low pathogenicity, low infectivity and a novel mode of transmission

Luis Marcelo Aranha Camargo — 2010-02-26T00:00:00Z

Background: Human capillariasis caused by Capillaria hepatica (syn. Calodium hepaticum) is a rare disease with no more than 40 cases registered around the world. Classically, the disease has severe symptoms that mimic acute hepatitis. Natural reservoirs of C. hepatica are urban rodents (Mus musculus and Rattus novergicus) that harbor their eggs in the liver. After examining the feces of 6 riverine inhabitants ( Rio Preto area , 8o 03'S and 62o 53' W to 8o 14'S and 62o 52'W) of the State of Rondonia, Brazil, and identifying C. hepatica eggs in their feces, the authors decided to investigate the real dimension of these findings by looking for two positive signals. Methods: Between June 1st and 15th, 2008, 246 out of 304 individuals were clinically examined. Blood samples were collected, kept under -20o C, and test by the indirect immunofluorescence technique. Results: The first positive signal was the presence of specific antibodies at 1:150 dilution, which indicates that the person is likely to have been exposed to eggs, most likely non-infective eggs, passing through the food chain or via contaminated food (total prevalence of 34.1%). A second more specific signal was the presence of antibodies at higher titers, thus indicating true infection. Conclusions: The authors concluded that only two subjects were really infected (prevalence of 0.81%); the rest was false-positives that were sensitized after consuming non-embryonated eggs.The present study is the first one carried out in a native Amazonian population and indicates the presence of antibodies against C. hepatica in this population. The results further suggest that the transmission of the parasite occurs by the ingestion of embryonated eggs from human feces and/or carcasses of wild animals. The authors propose a novel mode of transmission, describing the disease as a low pathogenic one, and showing low infectivity.

Natural infection of the sand fly Phlebotomus kazeruni by Trypanosoma species in Pakistan

Hirotomo Kato — 2010-02-25T00:00:00Z

The natural infection of phlebotomine sand flies by Leishmania parasites was surveyed in a desert area of Pakistan where cutaneous leishmaniasis is endemic. Out of 220 female sand flies dissected, one sand fly, Phlebotomus kazeruni, was positive for flagellates in the hindgut. Analyses of cytochrome b (cyt b), glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) and small subunit ribosomal RNA (SSU rRNA) gene sequences identified the parasite as a Trypanosoma species of probably a reptile or amphibian. This is the first report of phlebotomine sand flies naturally infected with a Trypanosoma species in Pakistan. The possible infection of sand flies with Trypanosoma species should be taken into consideration in epidemiological studies of vector species in areas where leishmaniasis is endemic.

Review of "Keys to the Nematode Parasites of Vertebrates. Supplementary Volume" by Lynda M. Gibbons

Frantisek Moravec — 2010-02-18T00:00:00Z

Book review of "Keys to the Nematode Parasites of Vertebrates. Supplementary Volume" by Lynda M. Gibbons

Mongolian and Japanese Joint Conference on "Echinococcosis: diagnosis, treatment and prevention in Mongolia" June 4, 2009

A Gurbadam — 2010-02-08T00:00:00Z

The first Mongolian-Japanese Joint Conference on "Echinococcosis: diagnosis, treatment and prevention in Mongolia" was held in Ulaanbaatar on June 4th, 2009. It was the first chance for Mongolian experts (clinicians, pathologists, parasitologists, biologists, epidemiologists, veterinarians and others working on echinococcosis) joined together. Increase in the number of cystic echinococcosis (CE) cases year by year was stressed. CE in children may be more than adult cases. Alveolar echinococcosis was suspected chronic malignant hepatic tumors or abscesses. Main discussion was as to how to introduce modern diagnostic tools for pre-surgical diagnosis, how to establish the national system for the data base of echinococcosis with the establishment of a network system by experts from different areas. The importance of molecular identification of the parasites in domestic and wild animals was also stressed.

Performance of circulating cathodic antigen (CCA) urine-dipsticks for rapid detection of intestinal schistosomiasis in schoolchildren from shoreline communities of Lake Victoria

C Standley — 2010-02-05T00:00:00Z

For disease surveillance and mapping within large-scale control programmes, RDTs are becoming popular. For intestinal schistosomiasis, a commercially available urine-dipstick which detects schistosome circulating cathodic antigen (CCA) in host urine is being increasingly applied, however, further validation is needed. In this study, we compared the CCA urine-dipstick test against double thick Kato-Katz faecal smears from 171 schoolchildren examined along the Tanzanian and Kenyan shorelines of Lake Victoria. Diagnostic methods were in broad agreement; the mean prevalence of intestinal schistosomiasis inferred by Kato-Katz examination was 68.6% (95% confidence intervals (CIs) = 60.7-75.7%) and 71.3% (95% CIs = 63.9-78.8%) by CCA urine-dipsticks. There were, however, difficulties in precisely 'calling' the CCA test result, particularly in discrimination of 'trace' reactions as either putative infection positive or putative infection negative, which has important bearing upon estimation of mean infection prevalence; considering 'trace' as infection positive mean prevalence was 94.2% (95% CIs = 89.5-97.2%). A positive association between increasing intensity of the CCA urine-dipstick test band and faecal egg count was observed. Assigning trace reactions as putative infection negative, overall diagnostic sensitivity (SS) of the CCA urine-dipstick was 87.7% (95% CIs = 80.6-93.0%), specificity (SP) was 68.1% (95% CIs = 54.3-80.0%), positive predictive value (PPV) was 86.1% (95% CIs = 78.8-91.7%) and negative predictive value (NPV) was 71.1% (95% CIs = 57.2-82.8%). To assist in objective defining of the CCA urine-dipstick result, we propose the use of a simple colour chart and conclude that the CCA urine-dipstick is a satisfactory alternative, or supplement, to Kato-Katz examination for rapid detection of intestinal schistosomiasis.