Species-Specific Adaptations of Trypanosome Morphology and Motility to the Mammalian Host.

African trypanosomes thrive in the bloodstream and tissue spaces of a wide range of mammalian hosts. Infections of cattle cause an enormous socio-economic burden in sub-Saharan Africa. A hallmark of the trypanosome lifestyle is the flagellate's incessant motion. This work details the cell motility behavior of the four livestock-parasites Trypanosoma vivax, T. brucei, T. evansi and T. congolense. The trypanosomes feature distinct swimming patterns, speeds and flagellar wave frequencies, although the basic mechanism of flagellar propulsion is conserved, as is shown by extended single flagellar beat analyses. Three-dimensional analyses of the trypanosomes expose a high degree of dynamic pleomorphism, typified by the 'cellular waveform'. This is a product of the flagellar oscillation, the chirality of the flagellum attachment and the stiffness of the trypanosome cell body. The waveforms are characteristic for each trypanosome species and are influenced by changes of the microenvironment, such as differences in viscosity and the presence of confining obstacles. The distinct cellular waveforms may be reflective of the actual anatomical niches the parasites populate within their mammalian host. T. vivax displays waveforms optimally aligned to the topology of the bloodstream, while the two subspecies T. brucei and T. evansi feature distinct cellular waveforms, both additionally adapted to motion in more confined environments such as tissue spaces. T. congolense reveals a small and stiff waveform, which makes these parasites weak swimmers and destined for cell adherence in low flow areas of the circulation. Thus, our experiments show that the differential dissemination and annidation of trypanosomes in their mammalian hosts may depend on the distinct swimming capabilities of the parasites.

Characterization of invasive and colonizing isolates of Streptococcus agalactiae in East African adults.

Ninety-five colonizing isolates and 74 invasive isolates of Streptococcus agalactiae from Kenyan adults were characterized by using capsular serotyping and multilocus sequence typing. Twenty-two sequence types clustering into five clonal complexes were found. Data support the view that S. agalactiae isolates belonging to a limited number of clonal complexes are invasive in adults worldwide.

Prevalence of Trypanosome Species in Cattle Near Ruma National Park, Lambwe Valley, Kenya: An Update From the Historical Focus for African Trypanosomosis.

The effective control of diseases in areas shared with wildlife depends on the validity of the epidemiologic parameters that guide interventions. Epidemiologic data on animal trypanosomosis in Lambwe valley are decades old, and the recent suspected outbreaks of the disease in the valley necessitate the urgent bridging of this data gap. This cross-sectional study estimated the prevalence of bovine trypanosomosis, identified risk factors, and investigated the occurrence of species with zoonotic potential in Lambwe valley. The area is ~324 km2, of which 120 km2 is the Ruma National Park. Blood was sampled from the jugular and marginal ear veins of 952 zebu cattle between December 2018 and February 2019 and tested for trypanosomes using the Buffy Coat Technique (BCT) and PCR-High-Resolution Melting (HRM) analysis of the 18S RNA locus. Risk factors for the disease were determined using logistic regression. The overall trypanosome prevalence was 11.0% by BCT [95% confidence interval (CI): 9.0-13.0] and 27.9% by PCR-HRM (95% CI: 25.1-30.8). With PCR-HRM as a reference, four species of trypanosomes were detected at prevalences of 12.7% for T. congolense savannah (95% CI: 10.6-14.8), 7.7% for T. brucei brucei (CI: 6.0-9.4), 8.7% for T. vivax (CI: 6.9-10.5), and 1.3% for T. theileri (CI: 0.6-2.0). About 2.4% of cattle had mixed infections (CI: 1.4-3.41). No human-infective trypanosomes were found. Infections clustered across villages but were not associated with animal age, sex, herd size, and distance from the park. Approximately 85% of infections occurred within 2 km of the park. These findings add to evidence that previous interventions eliminated human trypanosomosis but not bovine trypanosomosis. Risk-tailored intervention within 2 km of Ruma Park, especially in the north and south ends, coupled with stringent screening with molecular tools, could significantly reduce bovine trypanosomosis.

Pesticide pollution in freshwater paves the way for schistosomiasis transmission.

Schistosomiasis is a severe neglected tropical disease caused by trematodes and transmitted by freshwater snails. Snails are known to be highly tolerant to agricultural pesticides. However, little attention has been paid to the ecological consequences of pesticide pollution in areas endemic for schistosomiasis, where people live in close contact with non-sanitized freshwaters. In complementary laboratory and field studies on Kenyan inland areas along Lake Victoria, we show that pesticide pollution is a major driver in increasing the occurrence of host snails and thus the risk of schistosomiasis transmission. In the laboratory, snails showed higher insecticide tolerance to commonly found pesticides than associated invertebrates, in particular to the neonicotinoid Imidacloprid and the organophosphate Diazinon. In the field, we demonstrated at 48 sites that snails were present exclusively in habitats characterized by pesticide pollution and eutrophication. Our analysis revealed that insensitive snails dominated over their less tolerant competitors. The study shows for the first time that in the field, pesticide concentrations considered "safe" in environmental risk assessment have indirect effects on human health. Thus we conclude there is a need for rethinking the environmental risk of low pesticide concentrations and of integrating agricultural mitigation measures in the control of schistosomiasis.

Author Correction: Pesticide pollution in freshwater paves the way for schistosomiasis transmission.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The African trypanosome cyclophilin A homologue contains unusual conserved central and N-terminal domains and is developmentally regulated.

We have cloned and characterized the homologue of cyclophilin A (CypA) from Trypanosoma brucei brucei, Trypanosoma congolense, Trypanosoma evansi and Trypanosoma vivax. The 1-kilobase African trypanosome CypA complementary DNA contains an open reading frame of 531 base pairs, corresponding to 177 amino acids with a calculated molecular weight of 18,700. The CypA gene is present at one copy/haploid genome in T. brucei, T. congolense and T. vivax and is located on large chromosomes (>3 Mb) in T. brucei. CypA is differentially transcribed in African trypanosomes and is localized in the cytosol as well as in the flagellum. It is also detected in the supernatant of in vitro cultivated parasites. The African trypanosome CypA is unique due to a ten amino acid residue N-terminus extension and a block that includes a three amino acid insertion around position 100 that might result in a differently structured surface. Wild-type recombinant CypA and several mutants were over-expressed in Escherichia coli and purified to >98% homogeneity. Antisera from cattle immunized with a trypanosome fraction containing immunosuppressive activity react strongly against CypA. These data indicate that trypanosome CypA might play an important role in the establishment and maintenance of infections in susceptible animals.

Outbreaks of multidrug-resistant Acinetobacter baumannii strains in a Kenyan teaching hospital.

Acinetobacter baumannii is a serious nosocomial pathogen with a high propensity to cause outbreaks. Whilst outbreaks of A. baumannii have been reported in many regions worldwide, few data are available from East Africa. In this study, 25 A. baumannii isolates derived from a single institution located in Nairobi, Kenya, between September 2010 and September 2011 were examined. Antimicrobial susceptibility testing was performed by the disc diffusion method and the relatedness among the isolates was examined by pulsed-field gel electrophoresis, repetitive sequence-based PCR (rep-PCR) and multilocus sequence typing. The examined isolates clustered into three distinct groups. The most prevalent sequence type (ST) was ST110 (17 isolates), followed by ST92 (5 isolates) and ST109 (3 isolates). All isolates exhibited resistance to cefepime, ceftazidime, ticarcillin/clavulanic acid, cefotaxime/clavulanic acid, piperacillin/tazobactam, cefoxitin, ciprofloxacin, gentamicin, nitrofurantoin, fosfomycin trometamol, trimethoprim/sulfamethoxazole, amikacin, meropenem and imipenem, with the exception of four isolates. Two isolates belonging to ST92 and two isolates belonging to ST109 were susceptible to amikacin; one of these amikacin-susceptible ST109 isolates was also susceptible to meropenem and imipenem. All isolates were positive for OXA 51-like and all carbapenem-resistant isolates were OXA-23 positive.

Spatial distribution of African Animal Trypanosomiasis in Suba and Teso districts in Western Kenya.

BACKGROUND: Studies on the epidemiology of African Animal Trypanosomiasis (AAT) rarely consider the spatial dimension of disease prevalence. This problem is confounded by use of parasitological diagnostic methods of low sensitivity in field surveys. Here we report a study combining highly sensitive and species specific molecular diagnostic methods, and Geographical information system (GIS) for spatial analysis of trypanosome infection patterns, to better understand its epidemiology. Blood samples from 44 and 59 animals randomly selected from Teso and Suba districts respectively were screened for trypanosomes using PCR diagnostic assays. Spatial distribution of the positive cases was mapped and average nearest neighbour analysis used to determine the spatial pattern of trypanosome cases detected. FINDINGS: Trypanosome prevalence of 41% and 29% in Suba and Teso districts respectively was observed. T. vivax infections were most prevalent in both areas. Higher proportions of T. brucei infections (12%) were observed in Suba, a known sleeping sickness foci compared with 2% in Teso. Average nearest neighbour analysis showed the pattern of trypanosome infections as random. An overlay with tsetse maps showed cases lying outside the tsetse infested areas, mostly being cases of T. vivax which is known to be transmitted both biologically by tsetse and mechanically by biting flies. CONCLUSION: These findings suggest a need to design control strategies that target not just the biological vector tsetse, but also the parasite in cattle in order to clear the possibly mechanically transmitted T. vivax infections. There is need to also review the accuracy of available tsetse maps.

Comparative evaluation of three PCR base diagnostic assays for the detection of pathogenic trypanosomes in cattle blood.

Currently, several PCR based diagnostic assays have been developed to improve the detection of pathogenic trypanosomes. These tests include use of species specific primers, single and nested PCRs' based on primers amplifying the Internal Transcribed Spacer (ITS) regions of ribosomal DNA. This study compares three PCR based diagnostic assays and assesses the agreement of these three asaays by screening 103 cattle blood samples randomly collected from trypanosome endemic areas in western Kenya. The nested ITS based PCR, the single ITS based PCR and the species specific based PCR detected 28.1%, 26.2% and 10.7% of the samples respectively as positive for trypanosome infection. Nested ITS and single ITS PCRs' picked 3.8% and 1.9% as mixed infections respectively. Cohen kappa statistic used to compare agreements beyond chance between the assays showed highest degree of agreement (0.6) between the two ITS based tests, and the lowest (0.2) between the nested PCR test and the species specific PCR. The single ITS and nested ITS based diagnostic assays detected higher numbers of positive cases, and reduced the number of PCR reactions per sample to one and two respectively, compared to the five PCR reactions carried out using the species specific primers. This significantly reduced the labour, time and the cost of carrying out PCR tests, indicating the superiority of the ITS multi-species detection techniques. Reliable epidemiological studies are a prerequisite to designing effective tsetse and trypanosomiasis control programs. The present study established the suitability of using ITS based PCR assays for large-scale epidemiological studies.

A PCR based assay for detection and differentiation of African trypanosome species in blood.

Direct PCR analysis of trypanosome infected blood samples in the quantities required for large scale epidemiological study has always been problematic. Current methods for identifying and differentiating trypanosomes typically require several species-specific reactions, many of which rely on mouse passaged samples to obtain quality concentrated genomic DNA. As a consequence important epidemiological information may be lost during the sample preparation stage. Here, we report a PCR methodology that reduces processing and improves on the sensitivity of present screening methods. The PCR technique targets the gene encoding the small ribosomal subunit in order to identify and differentiate all clinically important African trypanosome species and some subspecies. The method is more economical, simple, and sensitive than current screening methods, and yields more detailed information, thereby making it a viable tool for large-scale epidemiological studies.