Serological changes observed in horses infected with Anoplocephala perfoliata after treatment with praziquantel and natural reinfection.
Authors: Abbott J B, Mellor D J, Barrett E J, Proudman C J, Love S
Journal: The Veterinary record
Summary
# Editorial Summary Anoplocephala perfoliata tapeworm infections in horses are common and clinically significant, yet our understanding of serological responses to treatment and reinfection remains limited. Abbott and colleagues tracked antibody levels and faecal shedding in two groups of naturally infected horses over 758 days: one receiving combination praziquantel (1.5 mg/kg) and ivermectin (200 µg/kg) therapy, and another receiving ivermectin monotherapy, to determine how serological markers correlate with actual parasite burden. Both groups showed declining antibody titres in the first month post-treatment, but the praziquantel-treated animals maintained significantly lower antibody levels through to day 121, whereas the ivermectin-only group's decline plateaued earlier; notably, antibody levels in the combination-treated group began rising again between days 151–295 despite negative faecal samples, with egg shedding reappearing in five of ten horses by day 295. These findings reveal that antibody titres do not reliably indicate current infection status in individual animals, as serological elevation can occur before tapeworms are detectable in faeces, and that ivermectin alone provides incomplete control of *A. perfoliata*, making combination therapy the superior choice—though practitioners should recognise that serology cannot be used as a sole marker of treatment efficacy or reinfection risk in this parasite.
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Practical Takeaways
- •Praziquantel + ivermectin clears A. perfoliata infection more completely than ivermectin alone, but horses can be naturally reinfected within 10 months
- •Antibody titres are a useful marker for tapeworm burden and can help identify reinfection; rising antibodies after initial decline suggest new infection rather than treatment failure
- •Monitor treated horses for serological and faecal signs of reinfection, as clinical management may need repeated treatment depending on pasture exposure and management practices
Key Findings
- •Antibody titres decreased from day 0 to day 28 in both treatment groups (praziquantel + ivermectin vs ivermectin alone)
- •Praziquantel + ivermectin group showed continued antibody decline through day 121, then significant increase from day 151–295
- •Eggs reappeared in faeces by day 295 in 5 of 10 animals in the combination treatment group, indicating natural reinfection
- •Serological response patterns differed between treatment groups, with praziquantel + ivermectin producing lower antibody levels before reinfection