1 06 2011




Wolbachia is a gram-negative intracellular bacterium associated with heartworms or (Dirofilaria immitis), as well as some additional filarial nematodes and some arthropods.


The Wolbachia bacteria are transmitted vertically from adult female heartworm to their offspring or microfilaria. There is a symbiotic relationship between the heartworm and the bacteria.  The Wolbachia infects all stage of the heartworm and is necessary for the development, reproduction and long-term survival of the parasite.


There is an apparent link between the inflammation associated with heartworm disease and the presence of the bacteria within the microfilaria.  The infected pet is protected from the bacteria as long as the heartworm is alive and well.  When the heartworm dies, for any reason, the Wolbachia organisms are release and inflammatory complications can occur.


Following the death of the heartworm there is a massive release of the bacteria into the tissues and bloodstream.  Severe inflammation may occur in the pulmonary artery endothelium followed by the formation of thrombi and interstitial inflammation. Wolbachia proteins have been shown to activate proinflammatory cytokines thereby increasing the inflammatory response.


Studies have shown that successful removal of the Wolbachia before heartworm treatment resulted in a significant reduction in pulmonary lesions following treatment.  There is evidence that treatment with tetracyclines during heartworm treatment may decrease the post treatment inflammation.


Studies have shown that pretreatment with tetracycline for30 days prior to adulticide treatment may result in suppressing microfilaria production and may be lethal to some of the adult D. immitis further decreasing the complications possible from heartworm treatment.







Bonagura, John and David Twedt, Editors.  Kirk’s Current Veterinary Therapy XIV.  Saunders/Elsevier. 2009. P. 841.


Todd-Jenkins, Karen.  “The Role of Wolbachia in Heartworm Disease.”  Veterinary Forum.  October 2007.  Pp. 28-29.



Wolbachia and their role in Heartworm Disease and Treatment

1 06 2011

Wolbachia and their role in Heartworm Disease and Treatment



Does your dog have heartworms or Dirofilaria immitis?  There is a long list of complications that may occur as a result of heartworm disease or the treatment thereof.  New research has shown that a gram-negative intracellular bacterium by the name of Wolbachia may be responsible for many of these complications and side-effects.


Wolbachia is a member of the family Rickettsiales.  This bacterium does not live outside of its host and is actually transmitted vertically from adult female heartworms to their offspring termed microfilaria.  A symbiotic relationship (mutually beneficial relationship) is believed to exist between the heartworm and the bacteria.  The Wolbachia infects all stages of the heartworm life cycle and is believed to be necessary for the development, reproduction and the long-term survival of the parasite


A direct relationship has been shown between the inflammation associated with heartworm disease and the presence of Wolbachia within the microfilaria.  A pet infected with heartworms is protected from the Wolbachia bacteria as long as the heartworm itself remains alive and well.  When that heartworm dies, from natural causes or heartworm treatment, the Wolbachia bacteria are released and severe inflammatory complications may result.


Following the death an adult heartworm, the Wolbachia bacteria are released into the bloodstream and body tissues in massive numbers.  The presence of these bacteria causes severe inflammation in the pulmonary artery endothelium which in turn may result in the formation of thrombi and interstitial inflammation.  Proteins found on the Wolbachia have also been shown to activate proinflammatory cytokines thereby causing an increase in the inflammatory response by the host.


Studies have shown that treatment with tetracyclines 30 days prior to adulticide heartworm treatment will be lethal to some of the adult D. immitis, suppress microfilaria production and when given following heartworm treatment may decrease the post treatment inflammation associated with the destruction of the parasite.







Bonagura, John and David Twedt, Editors.  Kirk’s Current Veterinary Therapy XIV.  Saunders/Elsevier. 2009. P. 841.


Todd-Jenkins, Karen.  “The Role of Wolbachia in Heartworm Disease.”  Veterinary Forum.  October 2007.  Pp. 28-29.



The Number One Behavior Problem Resulting in the Surrender of Pets to Animal Control Facilities and Tips for Preventing the Behavior Problem in the First Place

1 06 2011

The Number One Behavior Problem Resulting in the Surrender of Pets to Animal Control Facilities and Tips for Preventing the Behavior Problem in the First Place

A nationwide study of animal control facilities in 2000 showed that 40% of dogs and 28% of cats were surrendered due to one or more behavior problems and that number is thought to be much higher. The most common behavioral problem sited was inappropriate elimination. Owners are often reluctant to admit when there is a behavioral problem that results in the relinquishment of the pet because they believe acknowledging the problem will decrease the chance of the pet being adopted and increase the possibility of euthanasia.

Dogs that urinate at least weekly in the house are 2 to 4 times more likely to be turned into an animal shelter.  When cats urinate weekly in the house, they are 2 to 6 times more likely to end up being surrendered to an animal shelter.

In all cases of abnormal elimination a pet should be evaluated by their veterinarian first to determine whether a medical condition is the cause of the problem.  Bladder infections, diseases such as Diabetes or kidney failure which cause increased thirst and urination, etc. should be ruled out before settling on a behavior related diagnosis.  When abnormal bowl elimination occurs, parasites, pancreatitis, allergic colitis etc. should be ruled out as medical related problem before pursuing a behavioral change.

Most cats would prefer an unscented litter at a depth of 1 to 3 cm in their litter box.  Cats are much more sensitive to odors than are humans. When a cat does not dig enough in the litter box, they are sending the owner a warning signal that a problem exists.  Normally cats like to dig in the litter and cover up their elimination.  When cats dig in scented litter they tend to release additional odor which they may not appreciate.  Covered litter boxes also concentrate any odors in a small area and may be distasteful for a cat, especially when not cleaned frequently.  The litter box should be scooped daily and clumping litter should stay in the box no more than one month. Electronic litter boxes may effectively scoop the litter for you, allowing for a less frequent disposal of the scooped material.

Other litter box problems may include lack of privacy in multiple cat households.  It is not unusual for one cat to take advantage of another when they are in a compromising elimination posture.  Some cats may not appreciate sharing a litter box and will refuse to use it when it has been previously used by another.  With especially younger kittens, the litter box may not be in a convenient area and they will seek out a more readily available location in which to eliminate.  In these cases, the litter box may be moved to the site of elimination and gradually moved to a more out of site location.  Kittens, just like children, may become too wrapped up in what they are doing to seek out the bathroom facilities until it is too late to make it to the bathroom itself.

A host of new products are now available to attract cats to the litter box.  One such product is called Cat Attract® which is a formulation of herbs that may be used to literally “attract” the cat to the litter box area.

Spraying or the marking of territory with cats may be eliminated through neutering.  Multiple cat households often incur incidences of stress related marking.  Products for stress related marking includes Feliway® which mimics facial pheromones that give the cat a feeling of well-being and thereby eliminates stress.  When natural therapy is not enough, drugs are available to decrease stress and tension among cats in the household.  Your veterinarian will be able to help you with an appropriate choice of medication.

Male dogs also urinate on objects in order to mark territory.  Often this marking may be inhibited by neutering.  When neutering is not possible, belly bands with replaceable pads may be used.  DAP® (Dog Appeasing Pheromone), a product made to mimic calming pheromones in dogs, is also available to eliminate stress marking and works in much the same way as Feliway® for cats.

Adequate housetraining with puppies is a must!  One of the most common mistakes made by owners during housetraining is to allow elimination on pads or newspaper in the house when the owner expects the pet to go to the bathroom outside.  Dogs tend to get acclimated to a certain surface for elimination and once acclimated to that surface resist change.  When you want your dog to eliminate outside on the grass, start with grass on day one, otherwise the dog will come inside to use the bathroom just like everyone else in the family.  Another mistake made by new owners is to newspaper the entire bed area of the puppy.  The puppy will then eliminate immediately after being released from the confined area.  Puppies, much like us, prefer not to be confined with their waste material unless forced to.  It is appropriate for a puppy to want to keep their living area clean but not necessarily the rest of the house.  The behavior of keeping ones own house clean may be reinforced through the use of kennel training when the owner is not in attendance.  The kennel should be large enough to house the pet comfortably.  When forced to remain with their waste in a confined area, puppies will avoid eliminating unless absolutely necessary.  The owner can then capitalize on this behavior by taking the pet to a suitable site for elimination immediately upon release of the pet from the kennel.

Owners need to be realistic when using kennel training.  No puppy will be able to hold fecal and urine material for hours without having a necessary accident.  Puppies must be allowed out frequently or complicating problems may develop such as the consumption of personal waste by the puppy (being coprophagic) in an attempt to avoid being reprimanded by the owner for the elimination.  Owners must have realistic expectations regarding the length of time a pet may reasonably be confined before eliminating.  When it becomes necessary for puppies to be confined for long time periods, arrangements should be made to allow the pet to eliminate between reasonable periods, take them with you or they should be confined in fenced areas outside.

Additionally puppies should be allowed out to eliminate shortly after eating or immediately upon waking.

Dr. Bonnie Beaver, a past AVMA president states, “Behavior problems are the number one cause of euthanasia for dogs and cats.”  Approximately 10% of the total cat and dog population is euthanized each and every year. If we can inhibit elimination problems this figure is likely to decrease greatly.


“A Veterinary Medicine Interview Dr. Jacqueline C. Neilson”. Veterinary Medicine.  July 2007. p 436.

“Assist Owners in Selecting the Best Pets for their Lifestyles”.  The Compendium Continuing Education for Veterinarians. Vol 29(10). October 2007. Pp. 678.

Whipworms in the Dog

1 06 2011

Whipworms in the Dog



Does your dog have a bloody diarrhea? Make sure your veterinarian does multiple fecal samples checking for whipworms or Trichuris vulpis. The eggs of Trichuris are not as buoyant as the eggs of many other parasite species often necessitating that special procedures be used to confirm a diagnosis.  These thread-like inhabitants of the cecum have a bad habit of causing anemia, dehydration, even death in addition to a bloody diarrhea.  A recent study determined that 14.3% of the canine population may be infected.


The worm is actually whip-shaped, hence the name.  The worm embeds into the walls of the large intestine and cecum (a sac-like structure between the large and small intestines).  Female whipworms do not produce eggs every day but rather intermittently.  Compared to many species of parasites, female parasites produces only between 4,000 to 8,000 eggs per day when productive.  The eggs are passed out in the stool where they become infective first-stage larvae in as little as 9 to 10 days at 36°C or in as long as 25 days at an ambient temperature of 25°C.


Whipworms have what is termed a direct life-cycle involving only one susceptible host, a canine. The eggs are passed in the stool were an infective first-stage larva will develop within the egg but will not hatch unless swallowed by an appropriate host.  Once the larvated egg is ingested, the larva will be released in the small intestine were they then colonize the cecum and large intestine around 15 days after introduction.  After 3 months of development the female worms will begin intermittent shedding of eggs.


The prepatent period or the time between infection with Trichuris until the time when adult whipworms are producing eggs takes between 70 to 100 days.


The concept of intermittent shedding of eggs by the whipworm is important because multiple fecal analyses may be necessary to diagnosis the infection.  Clinical signs of infection may also be apparent before the appearance of eggs in the stool.  Diagnosis of a whipworm infection may therefore be difficult and may be made on clinical signs alone before conformation is possible.  Centrifugation of a stool sample is the most accurate type of fecal analysis currently available for whipworm diagnosis.


In a survey of shelter dogs, adult dogs were almost as susceptible to infection to Trichuris as were younger dogs.  Foxes and coyotes are both hosts for this parasite and will act as a reservoir for infection for domestic dogs.











Eggs may persist in the environment for up to 7 years, thereby making control difficult.  The eggs survive best in damp, shady areas of soil.


Treatments for whipworms include the following:  Febantel is an anthelmintic that may be found alone or in a combination drug by the name of Drontal Plus® developed from Bayer Animal Health. Fenbendazole is also an anthelmintic found alone in a product known as Safe-Guard® canine dewormer.  Safe-Guard is available from Intervet/Schering-Plough Animal Health.  Milbemycin is an anthelmintic and a heartworm preventative available from Novartis Animal Health by the name of Interceptor® or Sentinel®.  An additional anthelmintic/heartworm preventative containing moxidectin and Imidacloprid is available under the name of Advantage Multi® available from Bayer Animal Health.  When an anthelmintic is a heartworm preventative or used in combination with a heartworm preventative, the dog should be tested for heartworms and determined to test negative or be on a current and on an adequate heartworm preventative schedule already before beginning treatment.  The administration of a heartworm preventative in a heartworm positive canine may cause the development of a severe or even deadly allergic or anaphylactic to occur.  One treatment may be up to 90% effective, however due to the risk of reinfection, more than one treatment may be necessary.  Most treatment protocols involve multiple deworming at intervals of 3 to 4 weeks in duration.








Blagburn, Byron.  “The Elusive Whipworm, Trichuris vulpis.”  Clinician’s Brief.  September 2008.  P. 2-4.


Bowman, Dwight.  “A Clinical Overview of Whipworms.”  Veterinary Forum.  August 2008. Pp. 48-50, 70.

What Keeps Small Dogs Small?

1 06 2011

What Keeps Small Dogs Small?



Scientists from the University of Utah and others have identified a small piece of DNA that is a regulatory sequence termed the quantitative trait locus, not even a full gene that is located on a dog’s chromosome number 15 whose activity ensures that small breeds of dog stay small.  This sequence is located adjacent to the insulin-like growth factor 1 (IGF-1) gene. 


The IGF-1 hormone produces a growth factor that helps mammals grow.  A disabled version of the gene has been shown to produce small mice and has also been linked to a tiny person. The mutation in the regulatory sequence suppresses the gene’s activity in small dogs.  The dog is an ideal model for studying growth since they have the greatest diversity of size of any species of mammals.


All dogs weighing less than 20 pounds have been found to contain this regulatory sequence.









“Why Small Dogs are Small.”  Veterinary Forum, News Brief.  May 2007.  P. 16.

West Nile Virus in the Dog

1 06 2011

West Nile Virus in the Dog


West Nile virus is not very commonly seen in dogs with only 4 cases reported worldwide  through 2006, but 3 of these cases were reported in the U.S.


Patients exhibited tachycardia, pyrexia, stiff gait.  The dot may become tetraparetic and exhibited progressive neurologic clinical signs.  In addition these dots included signs of renal and hepatic failure.  Pancreatitis and synovitis has been reported resulting in a polyarthritis.


West Nile Virus should be considered as a differential diagnosis in any case of an antibiotic unresponsive fever, progressive neurologic camage and cardiac arrhythmias in the dog.


Confirmation may be achieved by rapid real-time RT-PCR assays of a biopsy or synovial fluid samples or IgM serology testing.






Cannon, AB, and AC Brault, et al .“Acute Encephalitis, Polyarthritis, and Myocarditis associated with West Nile Virus Infection in a Dog.”  Journal of Veterinary Internal Medicine 20:1219-1223, 2006.



Vaccine Reactions

1 06 2011

Vaccine Reactions




Vaccines are designed to induce immunity and prevent disease development in the vaccinated party. They have made some diseases rare and others almost nonexistent.  Through the use of vaccines we have saved an untold number of lives both human and animal. Unfortunately no vaccine is totally effective or completely free of adverse reactions


Clinical signs of vaccine reactions may vary with the type and intensity of the reaction.  Four types of vaccine reactions may occur.  Type I is known as an immediate hypersensitivity reaction or anaphylaxis (exaggerated allergic response).  Type II called a cytotoxic reaction that may exhibit as hemolysis (the destruction of red blood cells) or thrombocytopenia (lack of platelets) both resulting in bleeding or bruising by the affected animal.  Type III hypersensitivity occurs by immune complex formation, a typical example of which would be an anterior uveitis (inflammation in the anterior eye chamber). Reactions of this type were once seen after vaccination with canine hepatitis as clouding of the cornea or uveitis. This reaction has largely been eliminated with the newer vaccines.  Type IV hypersensitivity is a delayed reaction leading to granulomas (lump) formations at the site of the injection.


Several studies have tracked vaccine reactions both in the dog and the cat. In a study published in the AVMA journal, it demonstrated adverse vaccine reactions occurred at a rate of 38 per 10,000 dogs vaccinated.  According to this and other studies, the risk of reaction decreased significantly as the body weight of the pet increased.  Vaccines in the dog are given at a one dose fits all basis; this means a Great Dane would receive the some dose of vaccine given a 5 pound toy poodle. Not surprisingly, the 5 pound poodle would be more likely to incur a reaction to vaccination.  The risk of a vaccine reactions were also shown to increase significantly with the number of vaccine doses given concurrently during any one office visit.  Each additional vaccine given to a dog less than 22 pounds increased the risk of a reaction by 27% and for those over 22 pounds a 12% increase in risk was incurred.  A genetic predisposition to vaccine reactions has been documented for some particular breeds of dogs.  Neutering a pet also appeared to increase the number of adverse vaccine events and was thought to be due to the protective effect of androgen hormones.


In cats a vaccine adverse event rate was shown to be 51.6 reactions for each 10,000 cats vaccinated.  The risk was also shown to increase with the number of vaccines given per visit.  Once again cats weighing less or neutered cats appeared to be more susceptible to the possibility of a reaction.  The risk or reaction was greater for those cats over 1 year of age.  In this study almost a half a million cats were tracked for up to 2 years with none of these cats developing a neoplastic lesion.


The overall rate of vaccine adverse events occurring within 3 days of vaccination was determined to be 0.48% in cats and 0.38% in the dog.  The most common reactions were rather nonspecific reactions of anorexia (not-eating), lethargic, fever or local soreness.


Local vaccine reactions are common but are not true hypersensitivity reactions.  Local reactions include discomfort upon injection, irritation, pain and swelling at the injection site.  These types of reactions will usually resolve on their own.


The most severe type of adverse events are usually considered to be a type I hypersensitivity reactions.  Clinical signs with a type I hypersensitivity may be as mild, as an elevation in temperature, to severe, which includes shock and subsequent death.  Additional clinical signs of a type I hypersensitivity that may occur include; facial swelling or edema, pruritus, salivation, vomiting, diarrhea, difficulty breathing, or collapse and death.  Vaccine reactions of this type are less commonly seen in the cat verses the dog.  These types of vaccine adverse events are also commonly seen following vaccination in other species. Ferrets, in particular have a high rate of adverse events following vaccination.


Mild reactions usually respond to antihistamines and corticosteroids.  Severe reactions will require hospitalization and aggressive therapy including the use of epinephrine.


Delayed Hypersensitivity reactions are not uncommon and are typically exhibited as a lump that forms near the injection site.  Most will resolve within weeks of vaccination, especially when some moist heat or a warm compress is applied.  Moist heat may be applied simply by placing a washrag under the warm water faucet, wringing out the rag and applying it the site of the injection, making sure it is not too hot to handle as to cause discomfort.


Vaccine-associated fibrosarcomas (VAS) would be considered a type IV reaction and are a severe complication of vaccination.  Fibrosarcomas may occur in approximately 1 in 10,000 vaccinated cats.  VAS may also occur in the dog but at a much less frequent level than that seen in the cat.  The cause of fibrosarcoma development is still a matter of debate. Various vaccine components have been implicated but the research as to the cause has been inconclusive. There is a genetic mutation involving the p53 gene or the sis oncogene in cats that may predispose these animals to the formation of sarcomas.


Lumps occurring following vaccination should be subjected to the 3-2-1 rule according to the representatives at Merial.  If a lump meets any of these three criteria then a biopsy is warranted:


  1. The lump persists for more than 3 months after the injection.
  2. The lump is larger than 2 cm in diameter.
  3. The lump continues to increase in size 1 month after injection.


In order to decrease the occurrence of adverse vaccine events the “Feline Vaccine Advisory Panel” suggests that only cats that may be at risk for a certain disease should be vaccinated for that particular disease.  Each vaccine protocol should be tailored for each individual patient and their current lifestyle.  Risks and benefits will vary among patients dependent on the number of cats in the household, whether they are allowed outside, how frequent their exposure is to other cats, and if the pet is altered or used for breeding purposes.


General recommendations for decreasing the possibility of vaccine reaction regardless of species includes: vaccinating only healthy animals that have just completed a through comprehensive examination, premedicating with antihistamines, corticosteroids or both, separating the number of vaccines given and limiting vaccination to those vaccines that the pet is at risk for exposure.







“Feline Adverse Vaccine Reactions”.  The Compendium for Continuing Education for Veterinarians.  Merial Limited. Vol. 29(10) October 2007.  Pp.610 and 611.


“Vaccine Adverse Events”.  Antech Diagnostics News. October 2007.


Kahn, Cynthia Editor.  The Merck Veterinary Manual. 9th Edition. 2005. p. 637.