Equine trypanosomiasis, a systematic review: Disease management

Equine trypanosomiasis is a neglected protozoal disease.

To answer the study question: In equines what are the effects of disease management of trypanosomiasis on disease severity (individual level) and disease prevalence (population level) compared to no intervention?

Systematic review.

Studies were identified that described management of naturally occurring equine trypanosomiasis in any country following 'Preferred Reporting Items for Systematic Reviews and Meta-analyses' using eight international databases (1980-2022). Risk of bias was assessed using ROBINS-I. Data synthesis was descriptive.

Thirty studies were included (9 case reports, 5 case series, 15 cohorts, 1 randomised non-inferiority trial). Risk of bias was 'serious' (22/30), 'moderate' (7/30), 'low' (1/30). Heterogeneity was high. Disease severity (individual): Trypanosoma evansi: all evaluated trypanocides were effective in blood parasitaemia clearance (weak evidence). Clinical relapses were common (n = 60/241 equines treated; 25%) (strong evidence). Efficacy was poor once neurological signs were present (n = 12/19 equines; 63% mortality) (strong evidence). Trypanosoma equiperdum: a combination protocol could be curative before CNS invasion (weak evidence). Tsetse transmitted trypanosomiasis: Treatment of haemolymphatic disease with isometamidium or diminazene resulted in a positive clinical response (strong evidence). New/recrudescing infections were common in some regions (strong evidence). Trypanosoma vivax: treatment with high-dose diminazene had a poor clinical outcome (weak evidence). Disease prevalence (population): a multifaceted control programme was effective in reducing disease prevalence (weak evidence). Early (<2 days post-infection) treatment was more effective (weak evidence). Reported side effects were uncommon (n = 70/7888 equines; 1%) (strong evidence). Isometamidium chloride (0.5 mg/kg i.v.) can cause a shock response (13%; range 10-14; n = 14/105) (strong evidence).

Publication bias, heterogeneity, descriptive data.

Short-term trypanocide response for haemolymphatic disease was positive but optimisation of treatment protocols is required to reduce relapse and combat neurotrypanosomiasis. Reliance on trypanocidal treatment alone is common. Side effects are rare but can be severe.