Hookworms
Advocate®: Effective Against HookwormsHookworms are blood sucking nematode parasites of many mammalian species, including man. Hookworms are distributed world-wide and a major nematode infection causing clinical signs in dogs of all ages: Ancylostoma spp. is more prevalent in warmer climates, whilst Uncinaria sp. prefers temperate climates. The ParasitesThe name is derived from the distinctive „dentition“ of the parasite. The mouth cavity of Ancylostoma caninum and Ancylostoma tubaeforme has three pairs of sharp teeth at the ventral rim, while Uncinaria stenocephala lacks these teeth and the stoma is instead armed with rounded plates. A. caninum are the larger hookworms, with females measuring 15-18 mm and males 9-12 mm. In comparison, U. stenocephala females normally measure of 7-12 mm and males 4-5 mm in length.
Life CycleThe development of all hookworm species in the environment is rather similar. Hookworm eggs passed in dog or cats feces contain a 6-8 cell morula. The larva hatches from the egg and reaches the infectious stages after two molts. The development in the environment is highly temperature and humidity dependent and has been reported to be as short as 6-10 days. Ancylostoma is more prevalent in warmer climates, while Uncinaria is adapted well to the temperate climates and larvae are even able to survive over winter. It is these larvae in the environment that are the principle source of infection. Infection of the definitive host, the dog or cat, occurs in different ways depending on the species of hookworm and the age of the host animal. For Uncinaria stenocephala, infection occurs by means of the ingestion of larvae, while for Ancylostoma caninum, infection with larvae may occur via the oral, percutaneous or transmammary routes.
To watch or download the animation of the Canine/Feline Hookworm's life cycle please visit our download area. Pathogenesis and Clinical AppearanceHookworms are regarded as nematodes that feed on both blood and intestinal mucosa. Using the sharp teeth of the mouth cavity, they suck mucosal tissue and then digestion of the mucosa due to enzyme exposure occurs. While the mucosa is digested, underlying exposed small blood vessels burst and blood is released from the lesions. In a short time interval, the feeding nematode is attached to a new site, thus, after a brief period of time, mucosal lesions with petechial bleeding are visible. Experimental studies have shown daily blood intake from adult worms to be about 0.12 ml. The blood loss can lead to erythropenia, reduction of blood hemoglobin or decreased packed cell volumes. This microcytic hyprochrome anemia is due to the loss of iron. In addition, the loss of proteins adds to the severity of clinical signs. Clinical signs are highly dependent on the severity of worm burden, as well as age and nutritional status of the animal. Low to medium worm burdens may lead to wasting and reduced growth in puppies. Heavy worm burdens result in diarrhea containing fresh blood from mucosal lesions, and are a cause of death in highly infected litters. Cutaneous infection with larvae may cause erythema at the penetration sites. The clinical signs that follow are dependent on the migration of the larvae within the body tissue. For example, when larvae reach the brain, ataxia may be seen. Some authors classify the clinical signs of hookworm infections into three categories. A peracute infection occurs as a result of infection in nursing puppies via the milk of their mothers. An acute form with sudden exposure of high numbers of larvae can be found in older puppies and up to adulthood. The chronic stage is characterized by dogs infected with low numbers and shedding eggs, while clinical signs may be absent. It is commonly found with hookworms that their development in the host may be slowed by a variety of factors such as a sudden drop in temperature, hormonal imbalance of the host or intrinsic factors of the larvae itself. This is referred to as hypobiosis. Zoonotic significanceCutaneous larva migrans in man, also known as „creeping eruption“, is a dermatitis caused by migrating hookworm larvae. Infection occurs through skin contact with infective larvae and the most common sources of infection are shaded moist sandy areas or soil that has become contaminated via the feces of infected dogs or cats. The clinical symptoms in humans are erythema at the sites of infection and intensive pruritus. The severity, and also persistence, of the skin lesions are related to the immune status of the individual person. Hypersensitivity related to previous infection has been reported. Although a few cases of adult dog hookworms in the intestines of man have been reported, the risk of such infections does not appear widespread. DiagnosisDiagnosis of hookworm infection in very young puppies by fecal egg count (FEC) may be hard to detect because the mothers clean up the puppies’ feces right after defecation. Eggs of A. caninum (Fig.3) and U. stenocephala are soft-shelled nematode eggs, containing 4 – 8 cell morulae in fresh feces. In general, A. caninum eggs are shorter and larger in width than U. stenocephala. The size is recorded at about 53 –69 x 36 – 53 µm for A. caninum and 75 – 85 x 40 – 45 µm for U. stenocephala. However, although the diagnosis of a hookworm egg is easily done, species determination requires some experience. Today, polymerase chain reaction (PCR) techniques are in place to determine the presence of even low worm burdens and allow accurate species identification, although this is available in research or epidemiological studies, while performed less in general diagnostics.
Efficacy of Advocate® against adult hookwormsDogsStudies were performed to evaluate the efficacy of Advocate against U. stenocephala and A. caninum. These studies demonstrated that the product was 100% effective against patent infections of U. stenocephala and A. caninum.1,2,3,4 A study was also carried out to determine the persistence of activity of Advocate against U. stenocephala in dogs.5 Dogs were infected with L3 larvae of U. stenocephala 18 days after treatment with Advocate. During the post-treatment period, animals were observed daily for clinical signs. From day 30 post-treatment (12 days post-infection), daily fecal examinations were performed until day 39. A placebo-treated group was included as a control. No U. stenocephala were found in the dogs treated with Advocate 18 days pre-infection and the product was therefore shown to have persistent activity. CatsAs with hookworms in dogs, Advocate was found to be highly effective at eliminating A. tubaeforme, with studies again demonstrating 100% efficacy.6 In addition, a multi-centre field study revealed efficacy of 99.6% against hookworms, which compared very well with the positive control (Drontal Cat Tablets).7 Efficacy of Advocate® against immature hookwormsIn addition to demonstrating the efficacy of Advocate against the adult stages of A. caninum and U. stenocephala in dogs and A. tubaeforme in cats, work was carried out to assess the activity of Advocate against the L4 and immature adult stages of the hookworms listed above. DogsThe efficacy against immature stages of A. caninum and U. stenocephala was evaluated in experimentally infected dogs.8,9 Dogs were infected with larvae of both hookworm species on study day 0. Treatment was performed using the recommended label dosage at day 7 post-infection to determine efficacy against the L4 stage, and on day 11 post- infection for the immature adult stages. On final examination 5 - 6 days post-treatment, the efficacy against both hookworm species was determined (Table 1). Advocate proved to be 100% effective against both the L4 and immature adult stages. Table 1: % Efficacy of Advocate® against hookworms
CatsA similar study to the ones described above was carried out to assess the efficacy of Advocate against both the L4 and immature adult stages of A. tubaeforme (Table 2).10 Table 2: Efficacy of Advocate® against L4 and immature adults of A. tubaeforme in experimentally infected cats
ConclusionAdvocate® was found to be very effective at eliminating hookworms from both dogs and cats. This efficacy was demonstrated not only for the adult stages of A. caninum and U. stenocephala in dogs and A. tubaeforme in cats, but also for the L4 and immature adult stages of these hookworms. 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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Last changed: 19.11.2008 | ||||||||||||||||||||||||||||||||||||
