Hookworms in the Dog

1 06 2011

 

Hookworms in the Dog

 

 

 

Is your puppy anemic?  Does your dog appear to be losing weight and is the hair coat dull and thinning?  Have you noticed that your dog’s bowl movements are dark and tarry?  Then your pet may be suffering from a hookworm infection.

 

Hookworms are small thread-like worms that suck blood from the small intestinal tract of infected pets.  The most common types of hookworms infecting dogs include Ancylostoma caninum, Ancylostoma braziliense and Uncinaria stenocephala.

 

Puppies and nursing female dogs are at the highest risk for the development of a hookworm infection. As a dog becomes older they are typically more resistant to infection by hookworms.  Other factors determining the severity of an infection include: the virulence of the hookworm species, the ability of the dog to compensate for the blood loss caused by the hookworms, hematopoietic capacity or the ability of the infected pet to manufacture blood, the body condition of the individual at the time of infection and the presence or absence of any other stress on the dog.

 

Adult worms reside in the small intestinal tract of infected individuals passing their oval-shaped eggs out in the stool.  Infection occurs by the ingestion of the 3rd stage larvae from a contaminated environment, the penetration of intact skin by the infective larvae, the consumption of vertebrates with infective larvae in their tissues or through the milk of an infected mother dog to her puppies (transmammary infection).  An infected mother dog may transmit hookworm larvae in her milk for up to the next three lactations following infection.

 

Latent infections occur when the hookworm larvae arrest their development within the intestinal wall and skeletal muscle tissue of adult dogs serving as a reservoir for later infection.  This is believed to be especially common in mammary gland milk transfer of larvae to nursing puppies.  In other latent infections the larvae may migrate directly to the intestinal lumen or may migrate by way of the lungs to the intestinal tract.

 

 

 

 

 

 

 

 

 

 

 

 

 

Hookworm infections may appear quite diverse clinically. A hookworm infection may be inapparent to so severe, in peracute infections, that they result in severe anemia and even death.  Peracute infections are more commonly seen in young puppies through transmammary infection.  These puppies may appear healthy and sleek at birth but by the second week of life rapidly become anemic and deteriorate rapidly.  The feces will be very liquid and dark in appearance due to the presence of digested blood.  Eggs may not be apparent in a fecal analysis and therefore diagnosis must be made on the basis of clinical signs alone.  The prognosis in these cases may be guarded to poor regardless of the treatment used.

 

Sudden exposure to large numbers of infective larvae may result in an acute infection.  Fecal analysis may show large numbers of hookworm eggs to none at all.  The production of eggs may be preceded by clinical signs of infection by up to four days.  Clinical signs again include anemia and the presence of a dark-tarry stool or diarrhea.

 

Chronic infection with hookworms is typically asymptomatic.  Most cases are picked up on routine fecal analysis.  Still other chronic infections will show some degree of anemia, emaciation and in general an unthrifty or malnourished individual. 

 

The prepatent period or time from infection with third stage larvae until eggs are visible in the stool is 16 days.

 

One adult female hookworm can lay 25,000 to 30,000 eggs per day. Larva develops whenever the weather is favorable, typically in the late spring, summer and early autumn particularly when the mild weather is accompanied by adequate levels of rainfall. Favorite areas for larval development include gravel, sand and unpaved runs were the fecal material mixes with the soil.

 

Treatment involves an appropriate anthelmintic and in cases of severe anemia, a blood transfusion may become necessary.  Anemia caused by blood loss secondary to hookworms, especially in severely affected puppies, is often termed “hookworm anemia.”

 

Numerous products are effective against hookworms and include:  Nemex® manufactured by Pfizer, Rid Worm® marketed by Hartz, Drontal or Drontal Plus® produced by Bayer Animal Health, and Panacur C® marketed by Intervet to name a few products currently available.

 

 

 

 

 

 

 

 

 

Since hookworm eggs are not always detected on fecal analysis especially in young puppies and even peracute infections cannot sometimes be confirmed on a fecal, the “Companion Animal Parasite Council or CAPC,” advocates strategic deworming of puppies every 2 weeks from the time puppies are 2 weeks of age until they are eight weeks of age.  Thereafter the CAPC suggests the implication of a continuous program for parasite control.

 

Continuous control of hookworms in dogs is now possible through the use of various pharmaceutical products available as heartworm preventatives or combinations of a heartworm product and an anthelmintic, typically given monthly.  One such product, Advantage Multi®, is available from Bayer Animal Health.  Advantage Multi® is a combination of imidacloprid and moxidectin used topically for the control of heartworms, hookworms, roundworms, whipworms, ear mites, and fleas.  Additional

products for continuous control of hookworms include: Heartguard® which is marketed for the control of hookworms and heartworms and is available from Merial; Interceptor® or Sentinal®, from Novartis Animal Heath, which may be used for the prevention of heartworms, hookworms, whipworms and roundworms and in the case of Sentinal® is effective against fleas; Revolution®, a product from Pfizer Animal Health, available for the prevention of heartworms, hookworms, ear mites, and in the case of dogs some species of ticks as well as a product from Virbac called Iverhart Max®  which is effective against heartworms, hookworms, roundworms and the only heartworm product currently effective on tapeworms.

 

Sodium borate may be used for environmental hookworm larvae control at a rate of 10 lbs. per 100 sq. ft of surface area.  The sodium borate should be raked in the surface and will destroy the hookworm larvae in gravel or loamy surfaced runs.  The sodium borate will also destroy any vegetation present.

 

Paved surfaces, runs or kennels may be cleaned with a 1% sodium hypochlorite or Clorox solution.  This treatment will kill the larvae or leave them susceptible to environmental desiccation (drying out).

 

Zoonotic infection (transmission to humans) may occur through ingestion or by direct penetration of the skin by infective larvae.  Skin penetration often occurs by walking barefoot in a contaminated area, most of these cases are believed to originate at the beach.  Soft damp sand in front of beach buildings just above the high tide mark is an

 

 

 

 

 

 

 

 

 

 

 

ideal environment for the larvae development. Hookworm larval development is just but one reason dogs are not allowed on the beach in many areas.  The skin or cutaneous form

of hookworm infection occurring in humans is commonly termed “creeping eruption”, because migrating larvae produce a linear, tortuous (crooked), erythematous (red and inflamed) and intensely pruritic (itchy) eruption.  The parasite may travel from a fraction of an inch to several inches a day, typically moving more at night.

 

 

 

References:

 

“Continuous Control of Hookworms in Dogs and Cats.”  Clinician’s Brief.  July 2008 supplement.  July 2008. Pp. 1-8.

 

Georgi, Jay and Marion Georgi.  Parasitology for Veterinarians.  5th Edition.  1990. W.B. Saunders.  Pp. 172-177.

 

www.http.Virbac.com

 

Companion Animal Parasite Council (CAPC);www.capcvet.org

 

Centers for Disease Control and Prevention (CDC); www.cdc.gov

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