Protocol on deworming of pregnant females
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Ascarids are the most common helminths found in puppies and their mothers. Between 10-20% of dogs are infested, and this percentage rises to 60% in breeding kennels. Ascarids are considered zoonotic since humans, particularly children, can become infested by ingesting larvated eggs of Toxocara canis.
Although ascarids are not blood-feeding, they consume large amounts of glucose, amino acids, and vitamins. This nutritional depletion explains the bone deformities observed in heavily parasitized animals, as well as occasional convulsive episodes caused by hypoglycemia. Severe infestations can result in intestinal obstruction, occlusion, or perforation. The eggs excreted in feces are highly resistant, surviving temperatures between 10–45°C, desiccation, or moisture, and remaining infective for up to five years.
Parasite Life Cycle in Adult Animals
Understanding the parasite's life cycle is crucial for implementing preventive measures, especially in treating pregnant females. When eggs containing larvae are ingested by an adult dog, the larvae encyst in various organs. In males, the larvae die within months, but in females, they remain viable and reactivate during estrus. Once reactivated, they migrate to the lungs, mature into adult worms, and can infest puppies via the placenta or through colostrum and milk.
Puppies infested in utero begin hosting adult ascarids as early as 10 days of age due to the parasite's evolutionary cycle commencing before birth. Thus, three modes of infestation in young animals are identified:
- Transplacental Transmission: This can lead to ascariasis within the first 10 days after birth.
- Lactational Transmission: Milk ingestion can result in ascariasis by 5 weeks of age.
- Environmental Contamination: Eggs in the surroundings become infective by approximately one month of age, causing ascariasis by 8-9 weeks.
Clinical Signs
The following symptoms may be observed:
- Respiratory Symptoms: These correspond to larval migration through the lungs.
- Growth and Developmental Issues: Stunted growth, weight loss, irregular appetite, bone deformities (notably in large breeds), and hypoglycemic convulsions (especially in small breeds). These result from the parasite's nutritional depletion.
- Digestive Disturbances: Vomiting (potentially with expelled worms), alternating constipation and diarrhea, and abdominal distension. Without treatment, severe infestations can be fatal due to obstruction, perforation, or peritonitis.
Prophylactic Measures
Given the parasite's life cycle, the following medical prophylaxis is recommended:
Deworming of Pregnant Females
- At the start of estrus: To prevent larval reactivation.
- At day 40 of gestation: To block transplacental transmission, which begins at this stage.
- At delivery: To prevent lactational transmission.
- Every 15 days until weaning: To address reinfestation from environmental contamination.
Deworming of Puppies
- Initial Deworming:
- At 15 days in high-risk environments (kennels).
- At 3 weeks in isolated litters.
- Repeated Deworming: Every 15 days until weaning, then monthly until six months of age.
Sanitary Measures to Limit Environmental Contamination
- Avoid overcrowding.
- Use gravel or cement flooring instead of soil.
- Clean with high-pressure washing (e.g., pressure washer) and scrub corners and crevices.
Treatment
All traditional anthelmintics are effective against adult ascarids, but only fenbendazole (Panacur), flubendazole, oxfendazole, and levamisole are effective against encysted or migrating larvae. These vermicidal dewormers are therefore the most recommended.
The appropriate dosage for pregnant females is 50 mg/kg/day of fenbendazole for three days or 20 mg/kg/day for five days. This should be administered as outlined above: at the start of estrus, on day 40 of gestation, during delivery, and every 15 days until weaning.
Fenbendazole is a broad-spectrum oral anthelmintic with ovicidal, larvicidal, and vermicidal properties. It is safe for weak or cachectic animals and pregnant females at any stage of gestation. It can be administered to puppies as young as two weeks of age. Fenbendazole has no withdrawal period for milk and is administered orally using a syringe.
In addition to treating Toxocara canis in its mature and immature forms, fenbendazole is effective against mature Ancylostoma caninum, Uncinaria stenocephala, Toxocara cati, as well as mature and immature forms of Toxascaris leonina, Trichuris vulpis, Taenia pisiformis, Giardia sp., and Filaroides osleri.
Toxocara canis