Monday, January 14, 2013

Tick Fever of Dogs - Canine Babesiosis


Background

Canine Babesiosis is a protozoan disease caused by Babesia canis or Babesia gibsoni and is transmitted by ticks to susceptible canine hosts. It is one-celled organisms in red blood cells.  This disease is sometimes associated with other tick-borne diseases, such as Lyme disease, canine Ehrlichiosis, and Rocky Mountain spotted fever, among others. This can make symptoms worse and complicate diagnosis.

Canine Babesiosis occurs worldwide, mostly in regions where ticks are prevalent. Young pets tend to become infected most often, and with worse symptoms.

Pathogenesis

Animals are affected after an infected tick bites and feeds on a susceptible host for a minimum of three days.  When the Babesia organism is introduced into the host, it attaches to red blood cell membranes and is penetrated.  Hemolytic anemia and hypotensive shock are typical clinical syndromes of infection.  Hemolytic anemia results from direct erythrocyte damage by the parasite, and both intravascular and extravascular immune-mediated destruction of red blood cells.  
  
Clinical Signs & Symptoms
  • Loss of appetite
  • Lethargy
  • Fever greater than 105.8
  • Hemolytic anemia - Pale tongue, gums, and nose due to severe deficiency of red blood cells
  • Hematuria - Red or orange color urine
  • Enlarged lymph nodes
  • Icterus or jaundice - Yellowing of the skin and the whites of the eyes caused by an accumulation of bile pigment (bilirubin) in the blood
  • Splenomegaly &  Lymphadenomegaly


Diagnosis

Diagnosis begins with a complete history and a physical exam. Your veterinarian will most likely do the following:

History - Your veterinarian will likely inquire about recent tick exposure and bite history.
Complete Blood Count - These blood tests will evaluate various internal organ functions, including the heart, liver, kidneys, pancreas, metabolism, and electrolyte balance. The CBC is a measure of the amount and different kinds of red and white blood cells that are present in your dog’s body.

Blood Smear - This technique is used to examine the individual cells in your dog’s blood. Infection with B. canis or B. gibsoni is definitively diagnosed by demonstration of the parasites on red cells. Your veterinarian will use a drop of blood from your dog’s leg or neck, and spread it thin on a slide. They will then examine the slide under a microscope in order to see the Babesia parasite.

Immunofluorescence - This is a technique used to illuminate a pathogen or antibodies to a pathogen in a tissue or culture using a fluorescent dye. In this case, your veterinarian will make a tissue or cell smear and expose it to a specific antibody for Babesiosis. The dye will attach to any Babesia antibody displayed in the sample and show under a microscope as a bright green spot on the slide.
  
Treatment

Following are the most effective drugs used in the treatment of canine Babesiosis.  
  • Diminazene Aceturate,
  • Imidocarb Dipropionate
  • Clindamycin - Considered in refractory or more severe and virulent infections. 




Prevention

Prevention of canine Babesiosis is mostly aimed at controlling the vector.    The environment should be treated to decrease tick numbers, dogs should be treated to control tick infestations, and ticks should be removed from parasitized animals as quickly as detected.
Recently, a vaccine which minimizes the severity of infection was developed.  The vaccine is reported to be 70 to 100% effective in diminishing the pathologic effects which typically ensue upon infection. 
Blood transfusion poses a significant risk to recipient animals; therefore it is recommended that donor animals be tested for infection with Babesia organisms. 

Conclusion

It is important for practitioners to keep common diseases such as Babesiosis in the list of differential diagnoses for acute hemolytic anemia, shock and icterus.