AscaridsAdvocate®: Effective Against AscaridsAscarids are well known nematodes infecting domestic animals and man. The genera of interest in cats and dogs are Toxocara and Toxascaris. The ParasitesAscarids (maw worms) have adapted well to their particular hosts, which is reflected by their development pattern within the host and the routes of infection. A particularly good example of this is the dog roundworm, Toxocara canis, which can be transferred by several different routes, including the ingestion of embryonated eggs, ingestion of paratenic hosts, trans-placental transfer of larvae from the bitch to her unborn pups, and trans-mammary transfer wherein larvae pass from the bitch to the litter via the milk.
Life CycleThe adult worms live in the small intestine of dogs and cats, feeding on the intestinal contents and desquamated epithelial cells. Female roundworms produce eggs that pass out in the feces. The ascarid eggshell is capable of withstanding extreme environmental conditions and remains infective in soil for many years. The infective L3 larval stage develops within the eggshell and hosts can become infected by ingesting the egg with the infective larvae.
To watch or download the animation of the Feline/Canine Roundworm's life cycle please visit our download area. Pathogenesis and Clinical AppearanceDogs, as well as cats, heavily infected with adult Toxocara suffer from enteritis that can interfere with digestion and result in mal-absorption of food. Infection, especially in puppies and kittens, may be responsible for impaired growth and development, as well as clinical signs such as coughing, runny nose, vomiting after feeding, abdominal sensitivity to pressure, slimy unformed feces and even intestinal obstruction by entangled worms. Such heavily-infected animals commonly become jaundiced and emaciated and have a ruffled, unkempt coat. Young or adult dogs with mild infections are frequently asymptomatic or simply fail to gain weight. However, these animals remain important as a reservoir of infection, contaminating the environment and capable of passing the infection to other susceptible hosts, including man. Prenatal infection with T. canis results in abdominal pain in newborn puppies. Often the whole litter is affected and puppies remain agitated, making shrieking noises even after feeding. Immature as well as adult worms are passed with the feces or vomitus. However, this often goes unnoticed by the owner due to the bitches’ intensive cleaning habits. Death may occur in heavy infections due to rupture or obstruction of the intestine. Infection and somatic migration of larvae may cause hypersensitivity and allergic reactions. On haematological examination, eosinophilia would be the characteristic sign of infection. Zoonotic significanceIf a person accidentally swallows infective T. canis eggs from the environment, the parasite migrates through the body without undergoing development into an adult worm in the gut. This migration, known as „visceral larva migrans“, can cause serious disease if the larvae reach body tissues such as the brain or the eye. The dog or cat is not a direct source of infection to people, rather it is the egg deposition in the environment that causes a potential source of infection. Because eggs of T. canis remain infective in the soil for years, contaminated areas may become a hazardous source of visceral larva migrans infection, especially for children. Cases of visceral larva migrans from T. leonina have been reported, however, it seems to be of less importance than the risk from T. canis. DiagnosisThe eggs of T. canis are round in shape with a tick shell. The outer surface of this shell shows a characteristically rough surface (Fig. 4). In contrast, the egg surface of T. leonina is smooth (Fig. 5). These characteristics are used to differentiate between species. The eggs of both species measure 70-80 mm in diameter. Flotation methods are used to enrich eggs passed with the feces. For larval infection with Toxocara, serological enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody test (IFAT) methods have been described.
Efficacy of Advocate® against adult ascaridsDogsIn a series of clinical studies1-4, the efficacy of Advocate was evaluated for the treatment of patent T. canis and T. leonina infections in dogs. The results indicated that Advocate was 96–100% effective against T. canis and 97– 100% effective against T. leonina. Following on from this, a European multi-center field study compared the efficacy of Advocate with that of a positive control (Drontal Plus).5 Following the examination of fecal samples to look for the presence of nematode eggs, 131 worm-positive dogs were enrolled and allocated to one of two treatment groups. Prior to treatment a clinical examination, including an assessment for fleas, was carried out. At the end of the study, 8 to 13 days post-treatment, a second clinical examination was carried out and a second fecal sample taken for determination of fecal egg counts. Efficacy was assessed by comparing the fecal egg counts for the pre- and post-treatment samples, and revealed the following: Advocate was found to be very effective against infections of T. canis and hookworms, displaying efficacy of 98.8% and 99.9% respectively (Table 1). Table 1: % Efficacy against T. canis and hookworms
CatsAs with dogs, clinical and multi-center field studies6,7,8 were conducted to evaluate the efficacy of Advocate against patent T. cati infections. The results from the clinical studies demonstrated efficacy of 98.3% -100% against adult T. cati. A multi-center European field study9 was also carried out which compared the pre- and post-treatment fecal egg counts of cats receiving either Advocate or Drontal Cat Tablets. The results are shown in Table 2 below: Advocate showed itself to be as effective as Drontal Cat Tablets in removing T. cati and hookworms. Table 2: % Efficacy against T. cati and hookworms
Efficacy of Advocate® against immature AscaridsStudies were also performed to assess the activity of Advocate against the L4 and immature adult stages of T. canis and T. cati in dogs and cats, respectively.10-12 DogsThe efficacy of Advocate in dogs against L4 larvae and immature adult stages of T. canis was evaluated in experimental infections. Dogs were infected orally at study day 0 with a known number of infective stages of T. canis. Advocate was then applied at either day 14 or 24 post-infection. A placebo-treated group served as a control. The worm burdens were determined in animals of both groups 5 or 6 days after treatment – i.e. on day 19 or 20 post-infection for efficacy against L4, and on day 29 post-infection, for efficacy against immature adults. Two such studies were carried out in Europe and North America.10,11 The efficacy of Advocate was calculated in comparison to the control group and is shown in Table 3 below. Table 3: % Efficacy of Advocate® against L4 and immature adults of T. canis
CatsA similar study protocol to the one described above for dogs and T. canis was used for cats and T. cati to determine the efficacy of Advocate against L4 and immature adult stages12 (Table 4). Table 4: % Efficacy of Advocate® against L4 and immature adults of T. cati
ConclusionAdvocate® was found to be effective at eliminating not only adult stages of T. canis and T. cati, but also the L4 and immature adult stages, thereby comprehensively disrupting the lifecycles of the worms Questions about the product?If you have any questions about the product, please contact our Veterinary Service. References
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Animations for Download
Gripping life cycle animations of this parasite you'll find in the download area. |
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