Haematology of Experimental Trypanosoma Brucei Rhodesiense Infection in Vervet Monkeys

Haematological aberrations associated with human infective trypanosomes were investigated in the vervet monkey model of the Rhodesian sleeping sickness. Four monkeys were infected intravenously with 104 Trypanosoma brucei rhodesiense and monitored for changes in the blood profile using a haematological analyser. A chronic infection lasting between 48 and 112 days was observed. Microcytic hypochromic anaemia, which was characterized by a decline in packed cell volume (PCV), red blood cell (RBC) numbers, mean corpuscular volume (MCV) and mean corpuscular haemoglobin concentration (MCH) developed at an early stage, and persisted throughout the infection. The mean platelet counts declined significantly from 3 x 105/\u3bcl (day 0 post infection) to 6.8 x 104/\u3bcl (day 7 post infection) and remained low in all the animals. However, the mean platelets volume rose during the course of the infection. An initial decline in total white blood cell (WBC) counts occurred between day 0 and 7 (3.1 x 106/\u3bcl) and remained low up to day 35 post infection (3.5 x 106/\u3bcl). This was followed by an increase in WBC counts, principally associated with increased lymphocyte numbers. It is concluded that microcytic hypochromic anaemia, thrombocytopaenia and an initial leucocytopaenia are the most important haematological changes associated with a chronic infection of T.b. rhodesiense infection in vervet monkeys

Pharmacology of DB844, an Orally Active aza Analogue of Pafuramidine, in a Monkey Model of Second Stage Human African Trypanosomiasis

Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-y​l]-nicotinamide(DB820), exhibiting plasma Cmax values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.This investigation received financial support from the Bill and Melinda Gates Foundation through the Consortium for Parasitic Drug Development

<i>Trypanosoma brucei rhodesiense</i> transmitted by a single tsetse fly bite in vervet monkeys as a model of human African trypanosomiasis

Sleeping sickness is caused by a species of trypanosome blood parasite that is transmitted by tsetse flies. To understand better how infection with this parasite leads to disease, we provide here the most detailed description yet of the course of infection and disease onset in vervet monkeys. One infected tsetse fly was allowed to feed on each host individual, and in all cases infections were successful. The characteristics of infection and disease were similar in all hosts, but the rate of progression varied considerably. Parasites were first detected in the blood 4-10 days after infection, showing that migration of parasites from the site of fly bite was very rapid. Anaemia was a key feature of disease, with a reduction in the numbers and average size of red blood cells and associated decline in numbers of platelets and white blood cells. One to six weeks after infection, parasites were observed in the cerebrospinal fluid (CSF), indicating that they had moved from the blood into the brain; this was associated with a white cell infiltration. This study shows that fly-transmitted infection in vervets accurately mimics human disease and provides a robust model to understand better how sleeping sickness develops

Taenia solium Infections in a Rural Area of Eastern Zambia-A Community Based Study

Taenia solium taeniosis/cysticercosis is a zoonotic infection endemic in many developing countries, with humans as the definitive host (taeniosis) and pigs and humans as the intermediate hosts (cysticercosis). When humans act as the intermediate host, the result can be neurocysticercosis, which is associated with acquired epilepsy, considerable morbidity and even mortality. In Africa, most studies have been carried out in pigs with little or no data in humans available. In this human study, conducted in a rural community in Eastern Zambia, prevalences for taeniosis and cysticercosis were determined at 6.3% and 5.8% respectively, indicating the hyperendemicity of the area. Cysticercosis infection was strongly related with age, with a significant increase in prevalence occurring in individuals from the age of 30 onward. A collected tapeworm was confirmed to be T. solium. Risk factors associated with the transmission and maintenance of the parasite such as free roaming pigs, households without latrines, backyard slaughter of pigs without inspection and consumption of undercooked pork were also present. The findings of this work have identified the need for further research in the transmission dynamics and the burden that this infection has on the resources of poor local people

Virulence and pathogenicity of three <i>Trypanosoma brucei rhodesiense</i> stabilates in a Swiss white mouse model

Background: A key objective in basic research on human African trypanosomiasis (HAT) is developing a cheap and reliable experimental model of the disease for use in pathogenesis and drug studies. Objective: With a view to improving current models, a study was undertaken to characterise the virulence and pathogenicity of three Trypanosoma brucei rhodesiense stabilates, labelled as International Livestock Research Institute (ILRI)-2918, ILRI-3953, and Institute of Primate Research (IPR)-001, infected into Swiss white mice. Methods: Swiss white mice were infected intraperitoneally with trypanosomes and observedfor parasitaemia using wet blood smears obtained by tail snipping. Induction of late-stagedisease was undertaken using diminazene aceturate (40 mg/kg, Berenil) with curativetreatment done using melarsoprol (3.6 mg/kg, Arsobal). Results: The prepatent period for the stabilates ranged from three to four days with mean peak parasitaemia ranging from Log10 6.40 to 8.36. First peak parasitaemia for all stabilates varied between six and seven days post infection (DPI) followed by secondary latency in ILRI-2918 (15–17 DPI) and IPR-001 (17–19 DPI). Survival times ranged from six DPI (ILRI-3953) to 86 DPI (IPR-001). Hindleg paresis was observed in both ILRI-3953 (at peak parasitaemia) and ILRI-2918 (after relapse parasitaemia). Mice infected with IPR-001 survived until 54 DPI when curative treatment was undertaken. Conclusions: This study demonstrated that the stabilates ILRI-2918 and ILRI-3953 were unsuitable for modelling late-stage HAT in mice. The stabilate IPR-001 demonstrated the potential to induce chronic trypanosomiasis in Swiss white mice for use in development of a late-stage model of HAT

Risk factors associated with occurrence of nematodes in free range pigs in Busia District, Kenya

Nematode infections are a serious constraint to pig production, especially where free range pig keeping is practiced. This study investigated the epidemiology of nematodes in free range pigs in Busia District, Kenya. Three hundred and six pigs from 135 farms were sampled for faeces that were analysed for nematode eggs per gram (EPG) of faeces using the McMaster technique. The nematode eggs were also identified to genus and species based on morphology. A questionnaire on risk factors was also administered to the pig owners. The overall prevalence and mean nematode EPG were 84.2% and 2,355, respectively. The nematode eggs were identified as those belonging to Oesophagostomum spp. (75%), Strongyloides ransomi (37%), Ascaris suum (18%), Metastrongylus spp. (11%), Trichuris suis (7%) and Physocephalus sexalatus (3%). The prevalence of nematodes was positively correlated (p < 0.05) with the amount of rainfall in the division of the pigs' origin (all nematodes except S. ransomi). The prevalence of nematodes was also associated with the age of the pigs. A lower burden of nematodes was associated (p < 0.05) with a history of deworming (A. suum) and the provision of night housing (S. ransomi and Metastrongylus spp.). In conclusion, this study has provided information on nematode infections and the associated risk factors for free range pigs in Busia District, which can be used when implementing integrated control measures

Seroprevalence of Cysticercus cellulosae and associated risk factors in free-range pigs in Kenya

Porcine cysticercosis is an emerging zoonosis with public health and economic importance. A cross-sectional study was undertaken to investigate the disease in free-range pigs on 182 smallholder farms in Busia District, Kenya. The survey households were selected using a snowballing technique. Serum samples were obtained from 284 pigs of all ages at farm level and 37 pigs from slaughter slabs in the study area. The samples were analysed for the presence of cysticercus antigen using an antigen enzyme-linked immunosorbent assay (ELISA). A structured questionnaire was administered to determine the risk factors for porcine cysticercosis on the study farms. At pig level, the total number of pigs testing positive were 11, resulting in a seroprevalence of 4% (95% confidence interval (CI): 1.9–6.2%), while the farms with a positive pig were 9% (95% CI: 3.9–14.1%). All pigs examined in the slaughter slab survey were seronegative. The distribution of possible risk factors for porcine cysticercosis that were observed at farm level was as follows: free-range pig keeping (100%), history of human taeniosis infection in a family (51%), slaughtering of pigs at home (20%), lack of meat inspection (15%) and absence of latrines (15%). The only significant (χ2 = 4.4, P = 0.034, odds ratio (OR) = 3.8) risk factor associated with the occurrence of cysticercosis was lack of latrines at household level. The study shows that porcine cysticercosis is prevalent in free-range pigs in Busia District, Kenya and thus control measures need to be instituted

Relationship between the prevalence of ectoparasites and associated risk factors in free-range pigs in Kenya

A cross-sectional study was undertaken to determine the prevalence of ectoparasites and possible risk factors in free-range pigs from 135 farms of Busia District, Kenya.Three hundred and six pigs were examined for presence of external parasites using standard parasitological methods. Data on management practices including housing and history of acaricide spraying were also collected. The ectoparasites found in the pigs were Haematopinus suis (96.1%), Sarcoptes scabiei (63.7%), and ticks (29.7%). The tick species included Rhipicephalus appendiculatus (70%), Boophilus decoloratus (31%), and Amblyomma variegatum (12%). The occurrence of the infestations was associated with age, being highest in sows (S. scabiei) and finishers (ticks and H. suis). Male pigs had highest prevalences of H. suis and ticks, while female pigs had highest prevalence of S. scabiei.The prevalence of the parasitic infestations was significantly (P < 0.05) associated with their origin being either lower (H. suis and S. scabiei) or higher (ticks) in pigs originating from divisions with high rainfall. Housed pigs had significantly (P < 0.05) lower prevalence of H. suis and ticks than those from households without pig housing. It is concluded that the free-range pigs have high prevalence of ectoparasites, and effective control strategies focussing on improved animal husbandry and acaricide use should be implemented

Prevalence of gastrointestinal protozoa and association with risk factors in free-range pigs in Kenya

The current study investigated the occurrence of gastrointestinal tract (GIT) protozoa and associated risk factors in free range pigs in Busia District, Kenya. A total of 306 pigs from 135 farms in 6 Divisions were sampled for feces, which were analysed for parasites using direct smear and McMaster floatation methods. Associations between the occurrence of the parasites and explanatory variables (sex, age, division of origin and rainfall) were undertaken using ANOVA, chi-square and Pearson’s correlation statistics. The following gastrointestinal protozoan parasites were identified: Entamoeba spp. (87%), Balantidium coli (64%), Tritrichomonas suis (42%) and Coccidia spp (33%). The mean coccidial oocysts per gram (OPG) of all the sampled pigs was 1,276 (range = 0-28,000 OPG) and the proportions of the species included: Eimeria debliecki (40%), E. suis (26%), E. porci (16%), E. scabra (13%) and E. polita (5%). There was negative correlation between the amount of rainfall in the division of pig origin and prevalence of Eimeria spp, Tt. suis, and Entamoeba spp, but a positive correlation with prevalence of B. coli. The prevalences of Eimeria spp., Entamoeba spp. and Tt. suis were higher in males than females; but it was only the sex-differences for Tt. suis which were statistically significant (p < 0.05). The prevalences of Tt. suis in sows were significantly (p < 0.05) lower than that of growers and piglets. It was concluded that GIT protozoan parasites of economic and zoonotic significance occur in pigs in the study area and effective control strategies should be implemented

DNA-Detection Based Diagnostics for Taenia solium Cysticercosis in Porcine

Porcine cysticercosis is a neglected and underestimated disease caused by metacestode stage of the tapeworm, Taenia solium (T. solium). Pigs are the intermediate hosts of T. solium while human are the only known definitive host. The disease has an economic consequence because the affected farmers lose 50−100 percent of the value of pigs if they are infected. Lack of affordable, easy to use, sensitive, and specific molecular diagnostic tools for detection of infections at the farm level hinders the control of porcine cysticercosis in endemic areas. A number of DNA based diagnostic assays for the detection of T. solium infections in pigs have been developed and evaluated but none is applicable at low-resource areas where this disease is an endemic. This review focuses mainly on DNA based diagnostic methods, their sensitivity, specificity, and utilization at low-resource areas. We summarized data from 65 studies on the current DNA-detection based diagnostic techniques for T. solium cysticercosis in porcine, published in English between the years 2000–2018, identified through PubMed search engine. Of the different polymerase chain reaction (PCR) assays developed for identification of T. solium, the most sensitive (97−100%) and specific (100%) one is nested PCR. One study utilized loop-mediated isothermal amplification (LAMP) as a diagnostic tool for the detection of T. solium infections though its field use was never determined. Recombinase polymerase amplification (RPA) has been evaluated as a diagnostic tool for a variety of diseases, but has never been exploited for the diagnosis of cysticercosis/taeniasis. In conclusion, several molecular methods have been developed and evaluated in lab settings. However, there is need to validate these methods as a diagnostic tool to diagnose porcine cysticercosis in low-resource areas