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The term “unholy trinity” has been used to describe the three most common soil transmitted helminth infections in human medicine – ascariasis, trichuriasis, and hookworm infection. In a canine context the “unholy trinity” are better known as roundworm, hookworm and whipworm. Of these, Trichuris vulpis, the canine whipworm, is arguably the most frequently overlooked in clinical practice.
Life cycle
Adult whipworms are approximately 3-5 cm in length and bury their long thin anterior end into to the mucosal surface of the caecum and colon, leaving the thicker posterior tail segment protruding into the lumen. Each female worm produces more than 2,000 eggs per day which are passed in the faeces.1 Whipworm eggs are very resilient in the environment, remaining viable for years even under extreme environmental conditions.2 The prepatent period is 8 to 12 weeks.
Prevalence
In a recent study investigating the prevalence of canine intestinal worms in dog parks across Australia, whipworm was detected in 1.3% of faecal samples with a wide geographic distribution.3 Although not as prevalent as hookworm (10.2%), the prevalence of whipworm in this study was greater than that of roundworm which had a prevalence of 0.7%.
Clinical significance
Infestations can be associated with significant inflammation of the caecum and colon leading to mucoid or haemorrhagic large intestinal diarrhoea. In severe cases, hypoproteinaemia, anaemia and even death may result. Unlike roundworm, which is primarily a parasite of the young, studies have demonstrated an increased whipworm prevalence with age.4
Diagnosis
Diagnosing whipworm can be challenging for the following reasons:
• Whipworm has a long prepatent period (8 to 12 weeks) and dogs may show clinical signs before eggs are shed in faeces
• Egg shedding may be intermittent and egg numbers are lower than seen with other intestinal helminths (e.g., roundworm)
• Whipworm eggs are more dense than other species and therefore do not float as well in standard faecal flotations.
• Centrifuged faecal flotation is more sensitive but may still miss more than 50% of whipworm infestations.5
Commercially available antigen testing for whipworm overcomes a number of these challenges and greatly increases diagnostic sensitivity compared to faecal flotation.5
Treatment and control
The long prepatent period, high environmental resilience of shed eggs and lack of robust age-related immunity means whipworm is a risk for all dogs. Whipworm infestations can be treated with many, but not all, routine anthelmintics. Milbemycin oxime (0.5 mg/kg orally) and moxidectin (2.5 mg/ kg topically) are both effective against whipworm.2 Lower, oral doses of moxidectin have not been shown to be effective against whipworm.
As the prepatent period can be as short as 8 weeks, convenient monthly treatment with an endectoparasiticide that controls whipworm is ideal to minimise shedding and contamination of the environment with highly resilient eggs. Education of owners on the importance of the prompt removal of dog faeces from the environment is also important to reduce the environmental parasite burden.
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References:
1. Companion Animal Parasite Council Intestinal Parasites – Trichuris vulpis. Updated 12 Sept 2022. Accessed 1 October 2024. https://capcvet.org/guidelines/trichuris-vulpis/
2. Beugnet, F. et al. (2018). Textbook of Clinical Parasitology in Dogs and Cats. Servet editorial-Grupo Asís Biomedia, SL,.
3. Massetti, L. et al (2022) Faecal prevalence, distribution and risk factors associated with canine soil-transmitted helminths contaminating urban parks across Australia. Int J Parasitol. 52(10):637-646.
4. Gates, M. C. & Nolan, T. J. (2009) Endoparasite prevalence and recurrence across different age groups of dogs and cats. Vet Parasitol, 166, 153–158.
5. IDEXX Laboratories Technical update (2015). The Next Generation of Fecal Testing – Whipworm Antigen Testing. Accessed 1 October 2024. www.idexx.com.au/files/whipworm-diagnostic-update.pdf
