Ancylostomiasis

Ancylostomiasis is one of the widespread causes of morbidity and mortality in pups primarily due to their blood sucking activities in small intestine.

Etiology

• Ancylostoma caninum– principal cause of canine hookworm disease in most tropical and subtropical areas of the world.
• A. tubaeforme –cats.
• A. braziliense –dogs and cats.
• A. ceylanicum-dogs, cats and people.
• Uncinaria stenocephala-dogs and cats.
• These have worms have hook posture at anterior end, which is responsible for blood sucking activities in intestine.
• The infective larvae of canine hookworms, particularly those of A.braziliense, may penetrate and wander under the skin of people and cause cutaneous larva migrans.

Epidemiology

• Worldwide in the tropics and warm temperate areas.
• In endemic areas the disease is most common in dogs under one year old.
• In older animals, the gradual development of age resistance makes clinical disease less likely, particularly in dogs reared in endemic areas whose age resistance is reinforced by acquired immunity.
•  Predisposing factor- failure to removal of soiled bedding in kennels, damp, porous and cracked floors, can lead to a massive build-up of infection.

Transmission

• Ingestion of infective L₃ larvae from the environment.
• Skin (percutanous) penetration of infective L₃ larvae of A. caninum,  A. braziliense,  A.tubaeforme, or A. ceylanicum.
• Transmission of larvae of A.caninum  through colostrums or milk of infected bitches.
• Suckling of  new born pups on soiled mammary gland.

Life cycle

• Infection by either ingestion or skin penetration in young pups is followed by migration of the larvae through the blood to the lungs, where they moult to L₄ in bronchi and trachea, which is coughed up and swallowed then mature in the small intestine.
• However, animals >3 months old, A caninum larvae, after migration through the lungs, development are arrested in the somatic tissues (skeletal muscle)
• These arrested larvae are activated during pregnancy, then accumulate in the mammary glands. Arrested development may also occur in the mucosa of the small intestine; activation may occur after removal of adult worms from the intestine.
• The reactivated L₃ larvae passed in milk of bitch for 2 weeks after whelping.
• This trans mammary infection is often responsible for severe anemia in litters of young pups in their second or third week of life.
• Infection of the bitch on a single occasion has been shown to produce transmammary infections in at least three consecutive litters.

Pathogenesis

• The acute or chronic haemorrhagic anemia starts about 8^th day of infection in pups by plug feeding activities of immature adults on mucosa containing arterioles.
• Each worm removes about 0.l ml of blood within 24 hrs.

Clinical manifestation

• Anemia results directly from the blood sucking and the bleeding ulcerations at the site of bite.
• Intially acute normocytic, normochromic anemia followed by hypochromic, microcytic anemia in young puppies is the characteristic feature.
• Surviving puppies develop some immunity and show less severe clinical signs.
• Debilitated and malnourished animals may continue to be unthrifty and suffer from chronic anemia.
• Diarrhoea with dark, tarry faeces accompanies severe infections. Anemia, anorexia, emaciation, and weakness develop in chronic disease.
• Skin infection with U. stenocephala  causes dermatitis in the inter digital space.

Necropsy Findings

• Liver-fatty infiltration is seen.
• Lung consolidation.

Diagnosis

• Based on clinical signs.
• Presence of thin-shelled, oval eggs is readily seen in fresh faeces of infected animals either by centrifugation sedimentation/Floatation technique.
• Haematological analysis to confirm anaemia.

Treatment

• In dogs, fenbendazole, moxidectin, and pyrantel are approved for treatment of A caninum and U stenocephala infections.
• When anemia is severe, chemotherapy may have to be supported by blood transfusion or supplemental iron, followed by a high-protein diet until the hemoglobulin level become normal.
• When neonatal pups die due to hookworm infection, subsequent litters from the bitch should be treated weekly for A caninum for upto 12 wk beginning at 2 wk of age.
• In addition, fenbendazole (25 mg/kg, PO) given daily to pregnant bitches three weeks before whelping and two days after whelping greatly reduces transmammary transmission to the pups.
• Treatment of the bitch with ivermectin (0.5 mg/kg) on two occasions (4–9 days before whelping and 10 days later), or with moxidectin/imidacloprid spot-on on day 56 of pregnancy, has the same effect (extra-label use).

Control

• Weaned pups and adult dogs are treated every three month.
• Bitches should be free of hookworms before breeding and kept out of contaminated areas during pregnancy.
• Sanitary quarters should be provided for whelping and nursing bitches.
• Concrete runways that can be washed at least twice a week in warm water.
• Sunlit clay or sandy runways can be decontaminated with sodium borate (1 kg/2 m²).