Anoplocephala perfoliata in horses in Sweden: prevalence, infection levels and intestinal lesions.

The research investigated the prevalence, infection levels, and intestinal damage caused by the horse tapeworm Anoplocephala perfoliata in horses in Sweden. The study found that 65% of the examined horses were infected, with infection levels being higher in certain periods of the year, older horses, female horses, and specific horse breeds, and that the severity of the intestinal damage increased with the number of worms.

Study Methodology

• The study was conducted on 470 horses over a period of one year at an abattoir in central Sweden. Examination was focused on certain parts of the horse’s intestinal tract: the distal ileum, caecum, and proximal colon.
• Aspects like the infection levels of the horse tapeworm A. perfoliata, their development stage, site of attachment and the pathological lesions caused by the worm were all noted.
• From the total horses, fecal samples were taken from 395 of these horses and examined specifically for tapeworm segments and eggs, to correlate these findings with the numbers in the alimentary canal.

Major Findings

• The study found that 65% of the horses were infected with A. perfoliata, with an average of 79 worms per infected horse and a maximum of 912 worms.
• The level of infection varied significantly with factors including the time of year, the age of the horse, its gender, and its breed. Specifically, the infection was higher in the 3rd and 4th quarter of the year compared to the 1st and 2nd quarter; in older horses compared to yearlings; in females compared to males and geldings; and in thoroughbred and cold-blooded horses compared to Swedish standard breeds and ponies.
• The study also found that the use of certain drugs called anthelminthics against nematodes had no impact on the infection level.
• Out of the infected horses, 51% were found to have between 1-100 worms, while 14% were infected with more than 100 worms. As for the infection type, 72% of the infected horses had mixed infections consisting of both adult and juvenile worms, 20% had juvenile worms only, and 8% had adult worms only.
• Regarding intestinal damage, it was found that the severity of intestinal lesions increased with increasing numbers of A. perfoliata. About 11% of the intestines examined showed severe lesions. Interestingly, however, no cases of acute abdominal distress were reported in any of the examined horses.
• In terms of fecal examination, the number of detectable eggs were significantly higher for horses heavily infected with A. perfoliata, but the egg recovery rate among infected horses was only 35%.
• Lastly, an additional survey involving 218 horses on 88 premises in central and southern parts of Sweden revealed that the prevalence of A. perfoliata egg positive horses was the same as found on fecal examination during the abattoir survey.