Drug-resistant trypanosome isolates populations in dogs in Enugu North Senatorial Zone, Southeastern Nigeria

The impact of canine African trypanosomiasis in anti-poaching dogs in the Republic of Zambia

Zambia introduced canine units in 2014 as an anti-poaching tool. Working in challenging environments, these dogs face several health threats, one being the protozoal, vector-borne canine African trypanosomiasis (CAT). This report aims to investigate the incidence, management and impact of CAT on Zambia's canine units. Case data during 2019-2023 were collated to investigate incidence and clinical trends. A questionnaire examining mitigation methods and perceived impact of the disease was distributed. Participants, conservation organisations with canine units, were identified using non-probability, purposive sampling. Twenty-three cases were reported, deriving an incidence rate of 0.315 new cases per dog-year, with peaks in October and August. Pyrexia was reported in every case, and neurological signs in the two fatalities. Diagnostics included peripheral/buffy coat smears, polymerase chain reaction (PCR), and loop-mediated isothermal amplification (LAMP). Trypanocides used were isometamidium chloride (IC) and diminazene aceturate (DA). Current mitigation focused on vector control and chemical prophylaxis (using isometamidium chloride), with CAT cases reported during theoretical IC-covered periods. In conclusion, incidence and extensive mitigation methods highlight the significance of CAT in these valuable dogs. Clinical manifestations, adverse drug effects, and preventative methods all carry the potential to affect health, work and welfare. To ensure a sustainable future, research into risk-factors, molecular diagnostics, trypanocides, and prevention of CAT is of utmost importance.

Efficacy of a high dose of isometamidium chloride treatment in single and mixed experimental infections with T. congolense and T. brucei brucei in dogs

Canine African trypanosomosis is endemic in sub-Saharan Africa. Chemotherapy remains the commonly employed approach to trypanosomosis control. However, it is beleaguered by the absence of new drugs, treatment failures, relapse infection and resistance. The efficacy of a high dose of isometamidium chloride (ISM) in single and mixed infections of T. congolense and T. brucei brucei therapy was assessed in dogs. Fifteen dogs employed in this study were allocated into four groups at random, each with four dogs except group I which had three dogs. Group I dogs were not infected while groups II and III dogs received 106T. congolense and T. brucei brucei respectively. Group IV dogs received both (5 × 105) T. congolense and T. brucei brucei. Groups II-IV dogs were dosed with 1 mg/kg ISM (Trypamidium-Samorin®) intraperitoneally on day 14 post-infection (PI). Parasitaemia levels, live body weight changes (LBWC), clinical signs, rectal temperature (RT), some haematological and serum biochemical parameters were used to evaluate the efficacy of high dose of ISM. Following infection, all the infected dogs became parasitaemic by the 14th day PI, with obvious clinical signs. Treatment with ISM cleared parasitaemia within 72 hours post-treatment, caused the reversal of the clinical signs, and enhanced the RT, LBWC, haematological and serum biochemical parameters of the dogs. Relapse infection was not recorded throughout the study duration (84 days post-infection). In conclusion, 1 mg/kg of ISM is effective in treating African trypanosomosis in dogs and should be adopted as a first-line treatment for the disease.

Drug resistance in animal trypanosomiases: Epidemiology, mechanisms and control strategies

Animal trypanosomiasis (AT) is a complex of veterinary diseases known under various names such as nagana, surra, dourine and mal de caderas, depending on the country, the infecting trypanosome species and the host. AT is caused by parasites of the genus Trypanosoma, and the main species infecting domesticated animals are T. brucei brucei, T. b. rhodesiense, T. congolense, T. simiae, T. vivax, T. evansi and T. equiperdum. AT transmission, again depending on species, is through tsetse flies or common Stomoxys and tabanid flies or through copulation. Therefore, the geographical spread of all forms of AT together is not restricted to the habitat of a single vector like the tsetse fly and currently includes almost all of Africa, and most of South America and Asia. The disease is a threat to millions of companion and farm animals in these regions, creating a financial burden in the billions of dollars to developing economies as well as serious impacts on livestock rearing and food production. Despite the scale of these impacts, control of AT is neglected and under-resourced, with diagnosis and treatments being woefully inadequate and not improving for decades. As a result, neither the incidence of the disease, nor the effectiveness of treatment is documented in most endemic countries, although it is clear that there are serious issues of resistance to the few old drugs that are available. In this review we particularly look at the drugs, their application to the various forms of AT, and their mechanisms of action and resistance. We also discuss the spread of veterinary trypanocide resistance and its drivers, and highlight current and future strategies to combat it.

Comparative pathogenicity of single and mixed drug-resistant Trypanosoma brucei brucei and Trypanosoma congolense infections in rats

Drug-resistant trypanosomes are widespread in sub-Saharan Africa and in conjunction with the drug-sensitive phenotypes cause a serious endemic wasting disease in animals. We evaluated the pathogenicity of single and mixed drug-resistant Trypanosoma brucei brucei and T. congolense isolates in 35 female rats, randomly divided into seven groups (1-7) of five rats. Group 1 was the uninfected control. Groups 2 and 3 were infected with drug-sensitive T. brucei brucei and T. congolense, respectively, whereas groups 4 and 5 were infected with multidrug-resistant T. brucei brucei and T. congolense respectively. Group 6 were infected with drug-sensitive T. brucei brucei and T. congolense while group 7 were infected with multidrug-resistant T. brucei brucei and T. congolense. Parasitaemia kinetics, haematological parameters, body weight, clinical signs, survival time, gross and histopathological changes in the spleen were evaluated. Parasitaemia occurred between day 3-9 post-infection in all the infected groups. Rats in groups 4 and 7 had markedly prolonged (p < 0.05) pre-patent period, days to first peak parasitaemia, survival time, and lower (p < 0.05) parasitaemia level than groups 2 and 6 rats while these parameters were comparable for groups 3 and 5 rats. Anaemia was noted in the infected groups but the severity did not vary amongst the infected groups. Severe clinical signs and splenic lesions were noted in rats infected with drug-sensitive trypanosome species compared to the multidrug-resistant species. Therefore, we conclude that the trypanosome isolates were pathogenic. However, the drug-sensitive T. brucei brucei and mixed drug-sensitive trypanosome infections were more pathogenic than their multidrug-resistant counterparts.