Natural infection with Dictyocaulus arnfieldi in pony and donkey foals.

The research study examines the natural infection with Dictyocaulus arnfieldi in pony and donkey foals, demonstrating that exposure to a contaminated paddock results in patent lungworm infections in all subjects within a span of 11 weeks without any signs of respiratory disease.

Study Methodology and Results

• This research was conducted from June to October 1978, focusing on four pony mares and foals and two donkey mares and foals.
• All these subjects were grazing in a paddock that was contaminated with Dictyocaulus arnfieldi larvae which is a type of lungworm.
• Surprisingly, despite the infection, the foals did not show any visible signs of respiratory disease. However, within only 11 weeks of exposure to the paddock, all six foals developed patent lungworm infections which is an evident and detectable lungworm infection.
• In order to study the extent of the infection, one donkey and two pony foals were killed and subjected to a post mortem examination. Roundworms in different stages of development, even up to 8 cm long, were found in their lungs. This confirmed the presence of lungworms as a result of the exposure to the contaminated paddock.

Further Developments and Observations

• Post the examination, the remaining three foals were stabled for the further course of the study. Interestingly, two of these stabled foals displayed a halt in the excretion of D arnfieldi larvae during the winter months.
• However, one foal maintained the patent lungworm infection until the conclusion of the study the following year, in August 1979, demonstrating a persistent case of infection.
• Noticeably, the pony mares did not develop a patent lungworm infection, although two started to develop a cough around 4-6 weeks after beginning to graze in the infected paddock.
• A post-mortem examination of one such mare revealed the presence of small D arnfieldi (less than 7 mm). The other mare continued to exhibit a cough until the end of the study, that extended to over a year.

Thus, the study provides valuable insights into the impact and severity of the grazing in a D arnfieldi contaminated paddock on ponies and donkeys. The study also offers an understanding of the difference in the responses between adult animals and baby animals, implying a difference in resistance to the larvae.