Evaluation of different DNA extraction methods and loop-mediated isothermal amplification primers for the detection of Mycobacterium ulcerans in clinical specimens

BACKGROUND

Early diagnosis and treatment of Buruli ulcer is critical in order to avoid the debilitating effects of the disease. In this regard, the development of new diagnostic and point of care tools is encouraged. The loop-mediated isothermal amplification for the detection of Mycobacterium ulcerans represents one of the new tools with a good potential of being developed into a point of care test. There is however the need to standardize the assays, reduce sample preparation times, improve the detection/visualization system and optimize them for high-throughput screening, adaptable to low resourced laboratories.

METHODS

In this study, we assessed two DNA extraction protocols (modified Boom and EasyNAT methods), three previously published LAMP primer sets (BURULI, MU 2404 and BU-LAMP), and compared the sensitivity and specificity of LAMP assays on three DNA amplification platforms.

RESULTS

Our results show that Buruli ulcer diagnosis using primers targeting IS2404 for the LAMP method is sensitive (73.75-91.49%), depending on the DNA extraction method used. Even though the modified Boom DNA extraction method provided the best results, its instrumentation requirement prevent it from being field applicable. The EasyNAT method on the other hand is simpler and may represent the best method for DNA extraction in less resourced settings.

CONCLUSIONS

For further work on the development and use of LAMP tests for Buruli diagnosis, it is recommended that the BURULI sets of primers be used, as these yielded the best results in terms of sensitivity (87.50-91.49%) and specificity (89.23-100%), depending on the DNA extraction methods used.

Assessing Strategies Against Gambiense Sleeping Sickness Through Mathematical Modeling

Background

Control of gambiense sleeping sickness relies predominantly on passive and active screening of people, followed by treatment.

Methods

Mathematical modeling explores the potential of 3 complementary interventions in high- and low-transmission settings.

Results

Intervention strategies that included vector control are predicted to halt transmission most quickly. Targeted active screening, with better and more focused coverage, and enhanced passive surveillance, with improved access to diagnosis and treatment, are both estimated to avert many new infections but, when used alone, are unlikely to halt transmission before 2030 in high-risk settings.

Conclusions

There was general model consensus in the ranking of the 3 complementary interventions studied, although with discrepancies between the quantitative predictions due to differing epidemiological assumptions within the models. While these predictions provide generic insights into improving control, the most effective strategy in any situation depends on the specific epidemiology in the region and the associated costs.

Knowledge, attitudes and practices about human African trypanosomiasis and their implications in designing intervention strategies for Yei county, South Sudan

Background

A clear understanding of the knowledge, attitudes and practices (KAP) of a particular community is necessary in order to improve control of human African trypanosomiasis (HAT).New screening and diagnostic tools and strategies were introduced into South Sudan, as part of integrated delivery of primary healthcare. Knowledge and awareness on HAT, its new/improved screening and diagnostic tools, the places and processes of getting a confirmatory diagnosis and treatment are crucial to the success of this strategy.

Methodology

A KAP survey was carried out in Yei County, South Sudan, to identify gaps in community KAP and determine the preferred channels and sources of information on the disease. The cross-sectional KAP survey utilized questionnaires, complemented with key informant interviews and a focus group discussion to elicit communal as well as individual KAP on HAT.

Findings

Most (90%) of the respondents had general knowledge on HAT. Lower levels of education, gender and geographic locations without a history of HAT interventions were associated with incorrect knowledge and/or negative perceptions about the treatability of HAT. Symptoms appearing in the late stage were best known. A majority (97.2%) would seek treatment for HAT only in a health centre. However, qualitative data indicates that existing myths circulating in the popular imagination could influence people’s practices. Seventy-one percent of the respondents said they would offer social support to patients with HAT but qualitative data highlights that stigma still exists. Misconceptions and stigma can negatively influence the health seeking behaviour of HAT cases. In relation to communication, the top preferred and effective source of communication was radio (24%).

Conclusion

Gaps in relation to KAP on HAT still exist in the community. Perceptions on HAT, specifically myths and stigma, were key gaps that need to be bridged through effective education and communication strategies for HAT control alongside other interventions.

Misconceptions about sleeping sickness, a neglected tropical disease transmitted by tsetse flies, can be a hindrance to effective implementation of control interventions especially in the face of accelerating work to eliminate the disease. Understanding community knowledge, attitudes and practices about sleeping sickness is important in developing appropriate material for educating and sensitizing communities at risk of the disease. We conducted a study to establish community knowledge, attitudes and practices, including preferred channels of disseminating sleeping sickness information. Despite the fact that the community in Yei County knew about the disease, existing myths and stigma have the potential of influencing their health seeking behaviour.

The radio, community health workers and village elders were the most preferred sources of sharing information with the community. There is need to develop education and awareness material to address issues of existing myths, potential stigma, treat ability of HAT, importance of testing and treatment, as well as provide information on the new/improved testing and treatment approaches for HAT. In addition, this should be provided through use of preferred and trusted sources of information dissemination, which is critical in uptake of HAT control, management and prevention activities.

Cost-effectiveness of using a rapid diagnostic test to screen for human African trypanosomiasis in the Democratic Republic of the Congo

New rapid diagnostic tests (RDTs) for screening human African trypanosomiasis (HAT) have been introduced as alternatives to the card agglutination test for trypanosomiasis (CATT). One brand of RDT, the SD BIOLINE HAT RDT has been shown to have lower specificity but higher sensitivity than CATT, so to make a rational choice between screening strategies, a cost-effectiveness analysis is a key element. In this paper we estimate the relative cost-effectiveness of CATT and the RDT when implemented in the Democratic Republic of the Congo (DRC). Data on the epidemiological parameters and costs were collected as part of a larger study. These data were used to model three different diagnostic algorithms in mobile teams and fixed health facilities, and the relative cost-effectiveness was measured as the average cost per case diagnosed. In both fixed facilities and mobile teams, screening of participants using the SD BIOLINE HAT RDT followed by parasitological confirmation had a lower cost-effectiveness ratio than in algorithms using CATT. Algorithms using the RDT were cheaper by 112.54 (33.2%) and 88.54 (32.92%) US dollars per case diagnosed in mobile teams and fixed health facilities respectively, when compared with algorithms using CATT. Sensitivity analysis demonstrated that these conclusions were robust to a number of assumptions, and that the results can be scaled to smaller or larger facilities, and a range of prevalences. The RDT was the most cost-effective screening test in all realistic scenarios and detected more cases than CATT. Thus, on this basis, the SD BIOLINE HAT RDT could be considered as the most cost-effective option for use in routine screening for HAT in the DRC.

Analytical sensitivity and specificity of a loop-mediated isothermal amplification (LAMP) kit prototype for detection of Trypanosoma cruzi DNA in human blood samples

This study aimed to assess analytical parameters of a prototype LAMP kit that was designed for detection of Trypanosoma cruzi DNA in human blood. The prototype is based on the amplification of the highly repetitive satellite sequence of T.cruzi in microtubes containing dried reagents on the inside of the caps. The reaction is carried out at 65°C during 40 minutes. Calcein allows direct detection of amplified products with the naked eye. Inclusivity and selectivity were tested in purified DNA from Trypanosoma cruzi stocks belonging to the six discrete typing units (DTUs), in DNA from other protozoan parasites and in human DNA. Analytical sensitivity was estimated in serial dilutions of DNA samples from Sylvio X10 (Tc I) and CL Brener (Tc VI) stocks, as well as from EDTA-treated or heparinized blood samples spiked with known amounts of cultured epimastigotes (CL Brener). LAMP sensitivity was compared after DNA extraction using commercial fiberglass columns or after “Boil & Spin” rapid preparation. Moreover, the same DNA and EDTA-blood spiked samples were subjected to standardized qPCR based on the satellite DNA sequence for comparative purposes. A panel of peripheral blood specimens belonging to Chagas disease patients, including acute, congenital, chronic and reactivated cases (N = 23), as well as seronegative controls (N = 10) were evaluated by LAMP in comparison to qPCR. LAMP was able to amplify DNAs from T. cruzi stocks representative of the six DTUs, whereas it did not amplify DNAs from Leishmania sp, T. brucei sp, T. rangeli KPN+ and KPN-, P. falciparum and non-infected human DNA. Analytical sensitivity was 1x10^-2 fg/μL of both CL Brener and Sylvio X10 DNAs, whereas qPCR detected up to 1x 10⁻¹ fg/μL of CL Brener DNA and 1 fg/μl of Sylvio X10 DNA. LAMP detected 1x10^-2 parasite equivalents/mL in spiked EDTA blood and 1x10^-1 par.eq/mL in spiked heparinized blood using fiberglass columns for DNA extraction, whereas qPCR detected 1x10^-2 par.eq./mL in EDTA blood. Boil & Spin extraction allowed detection of 1x10^-2 par.eq /mL in spiked EDTA blood and 1 par.eq/ml in heparinized blood. LAMP was able to detect T.cruzi infection in peripheral blood samples collected from well-characterised seropositive patients, including acute, congenital, chronic and reactivated Chagas disease. To our knowledge, this is the first report of a prototype LAMP kit with appropriate analytical sensitivity for diagnosis of Chagas disease patients, and potentially useful for monitoring treatment response.

Trypanosoma cruzi, a parasite transmitted to humans from hematophagous insects, causes Chagas Disease, a Neglected Tropical Disease with public health impact, affecting 7 million people in Latin America. Although mainly related to low income populations inhabiting rural environments, migrations have conveyed Chagas Disease to urban areas of endemic and non-endemic countries. It often presents non-specific symptoms, and direct, low cost microscopy-based diagnosis only detects acute infections, missing a high proportion of cases. Serology is the “gold standard” diagnostic technique for chronic stages and needs the concordance of at least two different assays to confirm infection. In this context, we aimed to evaluate the analytical sensitivity and specificity of a prototype kit based on a novel and rapid molecular biology reaction, named Loop mediated isothermal amplification (LAMP), using standardized Real Time PCR as a comparator. To our knowledge, this is the first LAMP prototype kit with an analytical performance appropriate for human diagnosis of Chagas disease and potentially useful for monitoring treatment response. Its simple handling using basic laboratory devices will enable point-of-care diagnosis and screening for congenital infection at birth as well as early detection of acute infections due to oral contamination.

Evaluation of the diagnostic accuracy of prototype rapid tests for human African trypanosomiasis

Background

Diagnosis of human African trypanosomiasis (HAT) remains a challenge both for active screening, which is critical in control of the disease, and in the point-of-care scenario where early and accurate diagnosis is essential. Recently, the first field deployment of a lateral flow rapid diagnostic test (RDT) for HAT, “SD BIOLINE HAT” has taken place. In this study, we evaluated the performance of “SD BIOLINE HAT” and two new prototype RDTs.

Methodology/Principal Findings

The performance of “SD BIOLINE HAT” and 2 prototype RDTs was tested using archived plasma from 250 Trypanosoma brucei gambiense patients, and 250 endemic controls. As well as comparison of the sensitivity and specificity of each device, the performance of individual antigens was assessed and the hypothetical performance of novel antigen combinations extrapolated. Neither of the prototype devices were inferior in sensitivity or specificity to “SD BIOLINE HAT” (sensitivity 0.82±0.01, specificity 0.97±0.01, 95% CI) at the 5% margins, while one of the devices (BBI) had significantly superior sensitivity (0.88±0.03). Analysis of the performance of individual antigens was used to model new antigen combinations to be explored in development of the next generation of HAT RDTs. The modelling showed that an RDT using two recombinant antigens (rLiTat1.5 and rISG65) would give a performance similar to the best devices in this study, and would also offer the most robust performance under deteriorating field conditions.

Conclusions/Significance

Both “SD BIOLINE HAT” and the prototype devices performed comparably well to one another and also to the published performance range of the card agglutination test for trypanosomiasis in sensitivity and specificity. The performance of individual antigens enabled us to predict that an all-recombinant antigen RDT can be developed with an accuracy equivalent to “ SD BIOLINE HAT.” Such an RDT would have advantages in simplified manufacture, lower unit cost and assured reproducibility.

The most prevalent species of trypanosome causing human African trypanosomiasis (HAT), Trypanosoma brucei gambiense, presents a diagnostic challenge. While early diagnosis is essential for effective treatment and also to control transmission, symptoms are non-specific and parasitological diagnosis is laborious and technically difficult. Screening for HAT suspects has until now been done using the card agglutination test for trypanosomiasis (CATT), which requires a cold chain and equipment, making it difficult to deploy. Thus there is an urgent need for sensitive point of care diagnostic tests that are suitable for use in rural areas in terms of stability, simplicity and cost. We describe the evaluation of 3 rapid diagnostic tests (RDTs) for HAT based on lateral flow devices that detect antibodies against defined parasite antigens in blood samples. We demonstrate that the SD BIOLINE HAT RDT currently being deployed in HAT endemic regions, as well as two new prototype devices, are accurate in screening for HAT. By analysing the sensitivity of each of the antigens used in the devices tested, we predict that a highly sensitive RDT based on recombinant antigens can be developed. An all-recombinant antigen RDT offers significant benefits in manufacturing reproducibility and cost, and would dramatically simplify HAT diagnosis.

Economic assessment of the performance of trypanotolerant cattle breeds in a pastoral production system in Kenya

Cattle are the major source of food security and income for pastoral farmers in sub-Saharan Africa. However, infectious and parasitic diseases remain a major constraint to improved cattle productivity in the region. The use of animal health economics to support decision-making on cost-effective disease control options is increasingly becoming important in the developing world. Trypanotolerant indigenous Orma/zebu cattle in a trypanosomosis-endemic area of Kenya were evaluated for economic performance using gross-margin analysis and partial-farm budgeting. Orma/zebu and Sahiwal/zebu cross-bred cattle were exposed to similar husbandry practices and monitored for growth rate, incidence of common infections (trypanosomosis, anaplasmosis, babesiosis, East Coast Fever and helminthosis) and the cost of treatment assessed. Interview questionnaires were also used to assess the preference rating of the 2 breeds. Results indicated that incidence of infection was trypanosomosis 3%, anaplasmosis 58%, babesiosis 11%, East Coast Fever 22% and helminthosis 28%, with no significant difference between breeds. The Orma/zebu and Sahiwal/zebu breeds had comparable economic benefits, hence a pastoralist in Magadi division is likely to get similar returns from both breeds. This study therefore recommends adoption of not only the Sahiwal/zebu but also the Orma/zebu breed for cattle improvement in trypanosomosis endemic areas and conservation of indigenous genetic resources.

African trypanosomiasis: sensitive and rapid detection of the sub-genus Trypanozoon by loop-mediated isothermal amplification (LAMP) of parasite DNA

Control of human African trypanosomiasis (HAT) is dependent on accurate diagnosis and treatment of infected patients. However, sensitivities of tests in routine use are unsatisfactory, due to the characteristically low parasitaemias in naturally infected individuals. We have identified a conserved sequence in the repetitive insertion mobile element (RIME) of the sub-genus Trypanozoon and used it to design primers for a highly specific loop-mediated isothermal amplification (LAMP) test. The test was used to analyse Trypanozoon isolates and clinical samples from HAT patients. The RIME LAMP assay was performed at 62 degrees C using real-time PCR and a water bath. DNA amplification was detectable within 25min. All positive samples detected by gel electrophoresis or in real-time using SYTO-9 fluorescence dye could also be detected visually by addition of SYBR Green I to the product. The amplicon was unequivocally confirmed through restriction enzyme NdeI digestion, analysis of melt curves and sequencing. The analytical sensitivity of the RIME LAMP assay was equivalent to 0.001 trypanosomes/ml while that of classical PCR tests ranged from 0.1 to 1000 trypanosomes/ml. LAMP detected all 75 Trypanozoon isolates while TBR1 and two primers (specific for sub-genus Trypanozoon) showed a sensitivity of 86.9%. The SRA gene PCR detected 21 out of 40 Trypanosoma brucei rhodesiense isolates while Trypanosoma gambiense-specific glycoprotein primers (TgsGP) detected 11 out of 13 T. b. gambiense isolates. Using clinical samples, the LAMP test detected parasite DNA in 18 out of 20 samples which included using supernatant prepared from boiled blood, CSF and direct native serum. The sensitivity and reproducibility of the LAMP assay coupled with the ability to detect the results visually without the need for sophisticated equipment indicate that the technique has strong potential for detection of HAT in clinical settings. Since the LAMP test shows a high tolerance to different biological substances, determination of the appropriate protocols for processing the template to make it a user-friendly technique, prior to large scale evaluation, is needed.

Isolation and propagation of Trypanosoma brucei gambiense from sleeping sickness patients in south Sudan

This study aimed at isolating Trypanosoma brucei gambiense from human African trypanosomiasis (HAT) patients from south Sudan. Fifty HAT patients identified during active screening surveys were recruited, most of whom (49/50) were in second-stage disease. Blood and cerebrospinal fluid samples collected from the patients were cryopreserved using Triladyl as the cryomedium. The samples were stored at -150 degrees C in liquid nitrogen vapour in a dry shipper. Eighteen patient stabilates could be propagated in immunosuppressed Mastomys natalensis and/or SCID mice. Parasitaemia was highest in SCID mice. Further subpassages in M. natalensis increased the virulence of the trypanosomes and all 18 isolates recovered from M. natalensis or SCID mice became infective to other immunosuppressed mouse breeds. A comparison of immunosuppressed M. natalensis and Swiss White, C57/BL and BALB/c mice demonstrated that all rodent breeds were susceptible after the second subpassage and developed a parasitaemia >10(6)/ml by Day 5 post infection. The highest parasitaemias were achieved in C57/BL and BALB/c mice. These results indicate that propagation of T. b. gambiense isolates after initial isolation in immunosuppressed M. natalensis or SCID mice can be done in a range of immunosuppressed rodents.

Immunization of rabbits with Glossina pallidipes tsetse fly midgut proteins: Effects on the fly and trypanosome transmission

Proteins isolated from the midgut of Glossina pallidipes were used to immunize rabbits and their efficacy as vaccine candidate(s) against the fly, and their potential to block transmission of Trypanosoma brucei rhodesiense assessed. Two fractions, detergent (DET) and aqueous (AQ) fractions were separated using a non-ionic detergent (Triton X-114) and a series of bioassay experiments carried out using serum obtained from rabbits immunized with either of the two fractions. The mortality rates of tsetse flies fed on serum from rabbits immunized with DET and AQ was 56 and 35%, respectively, as compared to 20% mortality in controls. The DET antigen(s) caused considerably higher mortality (chi(2)=1.194, P<0.05) than that on controls. These findings suggest that midgut proteins contain antigens that are lethal to tsetse flies, and are potential candidates for the development of anti-tsetse vaccine. When flies fed on serum derived from DET immunized rabbits were fed on T. b. rhodesiense infected blood, only 20% of them picked the infection. Very few flies (20%) fed on serum derived from DET immunized rabbits had infection of T. b. rhodesiense. In the control flies 45% of them had infection in the midgut with a higher and actively motile parasite load. Assessment of fecundity indicated significantly higher (chi(2)=2.117, P<0.05) larviposition for the control flies when compared to the AQ group of flies (chi(2)=1.054, P<0.05). Significant differences in abortions and pupal weights were also observed. These results suggest that midgut proteins contain antigens with potential for use in development of vaccine to block transmission of trypanosomes through tsetse.

Detection of Trypanosoma evansi in camels using PCR and CATT/T. evansi tests in Kenya

Camel trypanosomosis (Surra) causes high morbidity and is an impediment to the camel husbandry in Kenya. The lack of a sensitive diagnostic test has hindered the collection of accurate epidemiological data and institution of control programmes. A cross-sectional study was conducted in three districts of Kenya to estimate the prevalence of Trypanosoma evansi (T. evansi) and to compare four diagnostic tests: polymerase chain reaction (PCR), card agglutination test (CATT/T. evansi), microhaematocrit centrifugation technique (MHCT) and mouse inoculation (MI). A total of 549 camels were randomly sampled. The overall prevalence of Surra was 5.3% using MHCT, 26.6% using PCR and 45.9% using CATT/T.evansi. There was a significant difference (P < 0.001) between PCR and CATT/T.evansi test, MHCT and MI in detection of T. evansi. The prevalence of T. evansi was 39.8% in Samburu, 24.7% in Nanyuki and 14.4% in Isiolo districts using PCR. A male camel was 2.6 times more likely to be infected with T. evansi compared to a female camel (OR = 3.0% CI: 1.6, 4.1), while an adult camel was 2.2 times more likely to be infected compared to non-adults (OR = 2.2; 95% CI: 1.2, 5.0). There was a poor association between the presence of the published clinical signs and seropositivity (kappa = 0.12), PCR (kappa = 0.11) and MHCT (kappa = 0.05). However, there was a higher agreement between farmers' classification of disease with the PCR test (kappa = 0.5, n = 61). The mean PCV varied with age, presence of infection, locality and gender, with the lowest mean PCV being recorded in MHCT-positive animals (20.97 +/- 0.5) and from infected calves (19.5 +/- 1.2). This study shows that PCR was more sensitive in detecting T. evansi than other tests used. Further, the prevalence of T. evansi in the camel herds sampled is higher than that previously reported in Kenya, and that the judgment by camel keepers may be a reliable "pen-side" diagnostic test for Surra. Considering the low sensitivity of parasitological techniques in detection of chronic T. evansi infection and high cost of PCR, development of a sensitive pen side diagnostic test, with a low cost is still a priority.

Growth and mortality in sheep and goats under high tsetse challenge in Kenya

Trypanosomosis is a major impediment to livestock production and economic development in those areas of Africa where it is endemic. Although small ruminants appear to perform better than cattle in various agro-ecological zones, the importance of trypanosomosis has not been extensively investigated in these livestock. This study was designed to investigate the prevalence of trypanosomosis in sheep and goats in an endemic area and to evaluate the performance of different breeds under high tsetse challenge and the potential role of chemoprophylaxis in the control of the disease. The results showed that tsetse flies feed readily on small ruminants, and that these animals are susceptible to trypanosomosis. The Small East African goats acquired fewer infections than the Black Head Persian and Dorper sheep used in the study. In both sheep and goats, chemoprophylaxis with isometamidium chloride (Samorin, Rhone Merieux, Annecy, France) was protective, resulting in fewer infections and higher body weight gain. Trypanosomosis caused anaemia in both sheep and goats, and animals whose PCV fell below 15% rarely recovered, even with trypanocidal drug treatment. The peak transmission period was between 1 and 3 months after the peak tsetse fly density, which raises the possibility of effective strategic prophylaxis.

Bowel function following primary repair of anorectal malformations at Kenyatta National Hospital

OBJECTIVES

To evaluate bowel function following primary repair of anorectal malformation.

DESIGN

A ten-year retrospective study.

SETTING

Kenyatta National Hospital, Nairobi, Kenya.

SUBJECTS

All patients with anorectal malformations attended to at Kenyatta National Hospital (KNH) within the study period who had posterior sagittal repair as a primary definitive procedure. All the children were over three years of age, toilet trained, and had their colostomies closed with an adaptation period of at least six months.

RESULTS

Posterior sagittal repair was used to repair anorectal malformations in 352 patients. One hundred and ninety three patients were evaluated. Overall voluntary bowel movement (VBM) was achieved in 71.5% of the patients, soiling was present in 21.2% of the patients and constipation in 7.3% of the patients. More than seventy nine per cent of children who had their colostomy fashioned before the age of one month achieved VBM, while 61.1% of the patients achieved VBM when the colostomy was fashioned after five years. Overall, 77.0% of the females achieved VBM compared to 63.8% of males. Patients with a perineal fistula achieved VBM in 79.1% of males and 75.0% of females, 76.0% with vestibular fistula, 73.9% with a recto-urethral fistula, 56.0% of anorectal anomalies without a fistula, 25.0% of vaginal fistulae and 12.5% in vesical fistulae. Overall patients with sacral defects achieved VBM in 25.9% compared to 78.9% in patients with a normal sacrum. The patients with low anomalies achieved VBM in 75.4% compared to 46.1% with high anomalies.

CONCLUSIONS

Posterior sagittal repair has been used to repair all anorectal malformations and has improved the quality of life of our patients, with better functional results expected in female patients, early colostomy fashioning and definitive repair, low or simple anomalies, and absence of sacral defects. The repair was associated with low morbidity and mortality.

The effects of drug-sensitive and drug-resistant Trypanosoma congolense infections on the pharmacokinetics of homidium in Boran cattle

Two groups of five Boran (Bos indicus) cattle were infected with one of two populations of Trypanosoma congolense; one drug-sensitive (IL1180), and one drug-resistant (IL3330). The animals were then treated intramuscularly with homidium bromide at a dose rate of 1.0 mg kg(-1) bodyweight 7 days after trypanosomes were detected in the peripheral blood of all the five animals in each group. Following treatment of cattle infected with drug-sensitive trypanosomes, parasites could no longer be detected in the bloodstream of four out of five cattle after 24 h, and after 48 h for the fifth animal. The animals remained aparasitaemic up to the end of the observation period of 90 days and serum drug concentrations determined by enzyme-linked immunosorbent assay (ELISA) remained above the detection limit of 0.1 ng ml(-1) for the entire period. Following treatment of cattle infected with drug-resistant trypanosomes, parasites did not disappear from the bloodstream in any of the five animals. The rate of drug elimination was greater in cattle infected with drug-resistant trypanosomes and the drug was no longer detectable approximately 3 weeks after treatment. Non-compartmental pharmacokinetic analysis showed that the values for t(12)beta of 75.5 +/- 16.9 h, the area under the curve (AUC(0-infinity)) of 1.33 +/- 0.156 microg h ml(-1) and the MRT(0-infinity) of 32.8 +/- 4.45 h obtained in cattle infected with the drug-resistant trypanosome population were significantly lower than the values of 424 +/- 146 h for t(12)beta, 1.67 +/- 0.233 microg h ml(-1) for AUC(0-infinity) and 297 +/- 159 h for MRT(0-infinity) obtained in cattle infected with the drug-sensitive population. The persistence of drug-resistant infections in cattle following homidium treatment was associated with more rapid drug elimination than in those in which infections with drug-sensitive parasites were cleared by the drug.

Standardised tests in mice and cattle for the detection of drug resistance in tsetse-transmitted trypanosomes of African domestic cattle

Resistance to the drugs used to control African animal trypanosomosis is increasingly recognised as a constraint to livestock production in sub-Saharan Africa. The most commonly used tests for detection of trypanocidal drug resistance are tests using mice or ruminants, but these suffer from lack of standardisation and hence it may be difficult to compare the results of different investigators. Tests in mice are less expensive than tests in ruminants, but while tests in mice they may be useful as a general guide to resistance in a geographic area they should not be extrapolated to cattle on an individual trypanosome level. Moreover, the commonly used protocols are too laborious for their application to large number of trypanosome isolates on an area-wide basis. This paper presents guidelines for standardised testing of trypanocidal drugs in vivo, and introduces a simplified single-dose test for use in mice, which is convenient for use in areas with limited laboratory facilities. The single-dose test is appropriate for characterisation of geographic areas in terms of trypanocidal drug resistance using large numbers of trypanosome isolates, for making comparisons between areas, and for monitoring changes in trypanocidal drug resistance over time. Multiple-dose tests may be used to determine the degree of resistance of individual stabilates to be determined precisely in mice are also described, but for logistical reasons these will rarely be conducted on more than a few stabilates, and testing of a larger number of stabilates in the single-dose test will generally provide more useful information. Finally, we describe tests in cattle that may be used to determine the efficacy of recommended curative doses of trypanocidal drugs for the treatment of infection with individual trypanosome isolates, including Trypanosoma vivax, which is rarely infective for mice.

Unravelling the phylogenetic relationships of African trypanosomes of suids

African trypanosomes of the subgenera Nannomonas and Pycnomonas have been recorded from both wild and domestic suids. However, complete descriptions of some of these trypanosomes with regard to host range, pathogenicity, transmission and distribution are still lacking. Neither the recently described Trypanosoma (Nannomonas) godfreyi nor Trypanosoma (Nannomonas) congolense Tsavo have been isolated from mammalian hosts, while Trypanosoma (Pycnomonas) suis remains the rarest of the Salivarian trypanosomes. The only isolate presumed to be of the latter species is maintained at the Kenya Trypanosomiasis Research Institute, Nairobi. We present here the results of characterization of this isolate by morphology, tsetse transmission, the use of species-specific DNA probes and DNA sequence analysis. Morphology in stained blood smears revealed a small trypanosome with a free flagellum. Experimental transmission through Glossina morsitans morsitans showed a developmental cycle typical of subgenus Nannomonas A positive identification was obtained with species-specific PCR primers for T. congolense Tsavo; moreover, the sequence of the SSU rRNA gene was almost identical to that of T. congolense Tsavo on database. In phylogenetic analysis of the SSU rRNA genes of Salivarian trypanosomes, T. congolense Tsavo grouped with T. simiae rather than T. congolense, suggesting that the name T. simiae Tsavo is more appropriate.

Comparative sensitivity of dot-ELISA, PCR and dissection method for the detection of trypanosome infections in tsetse flies (Diptera: glossinidae)

A visually read dot-enzyme linked immunosorbent assay (dot-ELISA) developed for the detection of trypanosomes in tsetse flies (Glossina spp.) was evaluated in the laboratory and under field conditions. In the evaluation, the fly dissection method was used as a standard technique and compared to the polymerase chain reaction (PCR). In laboratory studies, 133 and 126 tsetse flies were experimentally infected with different stocks of Trypanosoma brucei and T. congolense, respectively. Twenty-five days after infection, the flies were dissected and tested for the presence of trypanosomes using dot-ELISA and PCR. Dot-ELISA detected 98.4% of T. brucei and 94% of T. congolense infections in tsetse midguts, while PCR detected 97.6% of T. brucei and 96% of T. congolense tsetse midgut samples. For field evaluation of dot-ELISA, 700 tsetse flies were caught and screened for trypanosome infections by dissection. Seven of these (1%) had trypomastigotes in the midgut, 23 (3.3%) in the proboscis and none had trypanosomes in the salivary glands. All the flies with midgut infections also had trypanosomes in their proboscides. Five of the seven flies (71.4%) with midgut infections revealed by dissection, were also positive for T. congolense by the dot-ELISA and PCR techniques. Dot-ELISA detected T. congolense infections in an additional 86 (12.4%) of the 700 flies dissected. Of the 23 infections in the proboscis, 16 were T. vivax. Dot-ELISA detected 13 of the 16 (81%) while PCR detected 15 of 16 (94%) T. vivax infections. No T. brucei infection was detected by any of the methods in all the 700 tsetse flies examined. The results obtained from both the laboratory and field studies indicate that the dot-ELISA and PCR techniques are sensitive and species-specific in revealing trypanosome infections in tsetse flies. While dot-ELISA required a single test to detect T. congolense, several primer pairs were needed for PCR. The potential use of dot-ELISA as a tool for studying the epidemiology of trypanosomosis, while considering its field applicability and relatively lower cost is discussed.

Application of the Vettest 8008 system for the biochemical analysis of vervet monkey plasma

A clinical biochemistry analyser designed specifically for veterinary use was used to analyse plasma samples from 24 vervet monkeys (Cercopithecus aethiops). Two millilitres of heparinised blood was collected from each of the 24 monkeys on four occasions at intervals of one week. Plasma was separated and analysed for the concentrations of triglycerides, cholesterol, total proteins, albumin, globulins, creatinine and blood urea nitrogen (BUN) and the activities of alkaline phosphatase (AP), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatine kinase (CK). The tests were easy to perform, used small volumes of plasma, and yielded consistent results for most of the analytes. The activities of CK and AP, but not AST, appeared to be influenced by haemolysis, and there were significant individual variations in the activity of LDH.

Financial analysis of animal trypanosomiasis control using cypermethrin pour-on in Kenya

The financial impact of use of cypermethrin pour-on (Ectopor(R)) in control of animal trypanosomiosis was determined in a trial undertaken by the Kenya Trypanosomiasis Research Institute (KETRI). This trial started in December 1990 and ended in February 1992. It was undertaken in two adjacent ranches in the coast province of Kenya. The trial site was in an area of high apparent density (AD) of tsetse flies, and at the start of the trial no cattle were kept in this area. Cypermethrin was applied fortnightly to the 1100 steers which were kept in pour-on ranch 'A' while another 100 steers were kept in control ranch 'B' to act as control sentinels. From the main pour-on group, 100 animals were identified as the pour-on sentinels and compared to the control sentinels which received no pour-on.Pour-on application led to a significant decrease in the tsetse AD in the pour-on ranch A to 90% of the initial AD in some areas. The animals treated with pour-on had a significantly higher mean packed-cell volume (PCV). The weekly prevalence of trypanosome infections in animals treated with pour-on was <4% with only one exception when it was <10%. In the control animals, the prevalence ranged between 10 and 50% (with a few exceptions when it was <10%). The incidence of tick-borne diseases was lower in the pour-on animals. The mean monthly weights of the pour-on animals was significantly higher, and at the end of the trial the pour-on animals had a mean weight gain of 136.70+/-16.7kg while the control animals had gained 97.16+/-22.6kg. The financial net return of using cypermethrin pour-on was positive and the financial rate of return of 122.6% indicated that use of the pour-on was highly beneficial despite the high cost of the product.

Development and evaluation of an enzyme-linked immunosorbent assay (ELISA) for the determination of the trypanocidal drug homidium in serum of treated cattle

Two enzyme-linked immunosorbent assays (ELISA) for the determination of homidium in serum of treated cattle have been developed and evaluated. One is a direct competition (Assay 1) and the other an indirect competition assay (Assay 2). Both assays are highly sensitive with a limit of detection of 0.1 ng homidium per mL serum. Homidium levels were measurable in serum of cattle for over 2 months following administration of a single intramuscular (i.m.) dose at 1 mg/kg bodyweight. The level of sensitivity afforded by these assays makes them potentially useful tools in the pharmacokinetic evaluation of homidium and for investigating drug resistance or causes of drug failure. Assay 2 was chosen as being most suitable for further studies.

Some pharmacokinetic parameters of the trypanocidal drug homidium bromide in Friesian and Boran steers using an enzyme-linked immunosorbent assay (ELISA)

Pharmacokinetic studies on the trypanocidal drug homidium bromide using a competitive enzyme immunoassay (detection limit 0.1 ng/mL) are reported for non-infected Friesian and Boran steers following treatment with homidium bromide at a dose of 1.0 mg/kg b.w. Following intravenous (i.v.) treatment of Friesian steers (n = 5), the mean serum drug concentrations were 31.9 +/- 2.1 and 3.9 +/- 0.4 ng/mL at 1 and 24 h, respectively. The decline in serum drug concentration was tri-exponential with half-lives of 0.064 +/- 0.037 h for t1/2 alpha, 7.17 +/- 1.87 h for t1/2 beta and 106.3 +/- 6.6 h for t1/2 gamma for distribution and elimination phases 1 and 2, respectively. Drug was detectable in serum for 17 days following treatment. The mean residence time (MRT) was 63.4 +/- 7.5 h. Following intramuscular (i.m.) treatment of Friesian steers (n = 5), the drug concentration at 1 h after treatment was 72.5 +/- 2.2 ng/mL. This declined to 9.8 +/- 1.8 ng/mL at 24 h. Low concentrations of between 0.1 and 0.3 ng/mL remained in circulation for up to 90 days post-treatment. Following intramuscular treatment of Boran steers (n = 5), the mean serum drug concentration at 1 h after treatment was 112.1 +/- 40.3 ng/mL. By 24 h after treatment, the concentration had fallen to 13.0 +/- 3.3 ng/mL. Thereafter, the serum drug concentration-versus-time profile and the pharmacokinetic parameters obtained following non-compartmental analysis were similar to those obtained following intramuscular treatment of Friesian steers.

Changes in atrial natriuretic factor and plasma renin activity in dogs infected with Trypanosoma brucei

When beagle dogs were infected with Trypanosoma brucei, a marked reduction in the plasma concentration of atrial natriuretic factor (ANF) occurred in the terminal stage of the disease during weeks 3 and 4. At the same time there was an increase in plasma renin activity (PRA) after infection. Ultrastructural studies of the atria of these dogs demonstrated a reduction in ANF granules. The changes in ANF and PRA occurred in association with severe pancarditis and the development of heart failure. By impairing the ability of the heart and kidneys to regulate blood volume, the alterations in ANF and PRA could be involved in the pathogenesis of heart failure in T. brucei-infected dogs.

Elevation of the concentration of acute phase proteins in dogs infected with Trypanosoma brucei

Plasma concentrations of the acute phase proteins (APP), C-reactive protein (CRP) and haptoglobin (Hp), increased markedly following experimental infection of dogs with Trypanosoma brucei. The highest concentrations of CRP were observed immediately after peaks of parasitaemia. Treatment with curative doses of the trypanocidal drug suramin caused a rapid decrease in CRP. Relapse infections after subcurative treatment were followed by a reappearance of high plasma CRP concentrations. Haptoglobin remained elevated during the course of the disease. Curative treatment with suramin caused a gradual but slow decrease in Hp while subcurative treatment caused no significant changes. Thus, the estimation of CRP was useful in determining the presence of active infection and the success of chemotherapy. High Hp levels in severely anaemic dogs indicated that intravascular haemolysis does not contribute significantly to the anaemia associated with T. brucei infections in dogs. These conclusions need confirmation from a larger experiment.