Ancylostoma caninum infection in a Texas-born Blue Lacy dog — Alberta

Based on review of case records at the Western College of Veterinary Medicine, infection caused by the southern hookworm (Ancylostoma caninum) is relatively rare in western Canada. We report a recent case in a juvenile Blue Lacy dog, born in Texas.

A 53-day-old, male, Blue Lacy puppy was presented to a veterinary clinic in Leduc, Alberta, with a 2-day history of vomiting and lethargy. The dog had arrived in Alberta from Texas, clinically healthy, a few days prior to the onset of clinical signs. The 1st vaccination and deworming had reportedly been carried out in Texas. At its new home, the puppy had chewed a plastic ornamental plant and had had access to a live Dracaena massangeana plant, but ingestion of either was uncertain. There was no history of trauma or exposure to rodenticides. On one occasion after arrival, the dog had passed black, but formed, stool.

The physical examination revealed 5% to 8% dehydration, slight obtundation, grayish oral mucus membranes, and pale pink conjunctiva. The temperature was 38.6°C and the heart rate was 180 beats/min. A grade I/VI systolic heart murmur was noted. No signs of pain were elicited by abdominal palpation. A tentative diagnosis of gastrointestinal blood loss due to parasites or an ulcer was established. Blood and fecal samples were collected; grossly, the blood sample was watery and pale red. Intravenous lactated Ringer’s fluid therapy was commenced and the dog received metoclopramide HCl (Metoclopramid Hydrochloride; Sandoz Canada, Boucherville, Quebec) 0.2 mg/kg bodyweight (BW), SC, q6h; ranitidine (Zantac; Glaxo Smith Kline, Mississauga, Ontario), 2 mg/kg BW, IV, q8h; and ampicillin (Ampicillin Sodium; Novopharm, Toronto, Ontario), 22 mg/kg BW, IV, q8h. Results from the complete blood (cell) count (CBC) revealed severe normochromic, macrocytic regenerative anemia (Hct 0.09 L/L, normal 0.36 to 0.57 L/L) highly suggestive of parasitic infection. Results from fecal flotations were positive for hookworm eggs. Despite aggressive therapy, the dog died 2 d later.

The postmortem examination revealed a well-conditioned carcass. The oral mucosa, nictitating membrane, and skeletal musculature were pale tan-pink. The serosa of the small intestines had multiple, variably sized hemorrhages; whereas, the mucosa was diffusely hemorrhagic. The jejunum and ileum were distended with watery, blood-tinged fluid containing a myriad of adult nematodes, some still firmly attached to the intestinal mucosa. The grayish parasites, averaging about 1 cm in length, resembled fine thread. Based principally on the morphology of the stoma (3 pairs of sharp teeth), platymyarian musculature, thick cuticle, and lateral internal cuticular ridge, the adult nematodes were identified as southern hookworms (Ancylostoma caninum). Fecal flotation established 4+ presence of southern hookworm eggs.

Microscopically, the ileum had several cross-sectioned hookworm adults and eggs surrounded by abundant hemorrhage (Figure 1). Further examination revealed a spectacular image of an adult parasite attached by the stoma to an intestinal jejunal villus (Figure 2). Parenchymatous tissues were completely devoid of blood. In addition, the hepatocytes of all periacinar zones displayed evidence of degeneration and necrosis, consistent with anemic hypoxia.

Figure 1.

The jejunal lumen contains 2 cross sections of adult parasites (arrows) and 3 eggs (arrow points). Note the backdrop of heavy hemorrhage, serum, and sloughed epithelia. Bar = 250 μm.

Figure 2.

An unusual longitudinal section of a feeding adult Ancylostoma caninum. Note the teeth (arrows) embedded into an intestinal villus. Bar = 100 μm.

Unlike infections with the less pathogenic northern hookworm (Uncinaria stenocephala), the infections caused by the southern hookworm are rare in western Canada. A search of Prairie Diagnostic Services computer records between 1991 and 2007 produced 15 cases. Only 1 dog showed clinical signs similar to those described in this report. The owners of 4 additional animals reported signs ranging from soft stool and presence of worms in feces to sudden anorexia. Most of the cases presented for diagnostic evaluation did not have any history. Except for 2002, each year had a single case of hookworm infection. Interestingly, as of January, 2007, 2 cases have been recorded. Four of 15 cases were linked to animals originating from, or traveling to and from, California, South Carolina, Texas, or some unidentified location in the southern USA.

The infection with Ancylostoma spp. may occur perorally, percutaneously, or transmammarily. The infection is most severe in young dogs raised in unsanitary conditions. Hookworms feed on small intestinal mucosa consuming about 0.1 to 0.8 mL of blood/d. They often change the site of attachment, leaving a bleeding site behind. In addition, A. caninum constitutes an important zoonosis, as the larvae can invade human skin (cutaneous larva migrans), resulting in itchy, serpiginous skin eruptions, usually found on the hands and legs.

This case illustrates that even though rare in western Canada, infection caused by A. caninum should be considered as a differential diagnosis in young anemic dogs historically linked to warmer and more humid parts of the world.