Canine Leptospirosis
by Sarah Levine, VMD
Leptospirosis, a spirochetal disease that occurs worldwide in numerous animal hosts, is re-emerging as an important zoonotic disease. Reported cases are on the rise throughout the world. Different serovars of Leptospira interrogans are maintained in nature in numerous sub-clinically infected wild and domestic animal reservoir hosts. Reservoir hosts are a source of infection for humans and other incidental hosts(1).
The canine disease presents as an acute infection of the kidney and liver and even as a septicemia. Chronic kidney disease is a common manifestation of infection. Abortions may occur in pregnant bitches. The prevalence of Leptospirosis in dogs may be underestimated because of asymptomatic infection.
Leptospirosis is influenced by the cycles of infection in wildlife, where the infection may spill over into domestic animal populations(2). Canine infection is seen mostly in hunting and sporting dogs that eat wildlife, or dogs that have access to wooded areas with riverbanks or marshes. Standing water is a natural environment for Leptospira. Infection occurs via direct contact with contaminated urine and by transplacental and venereal routs. Indirect infection is also possible via exposure to contaminated water, vegetation, soil or food.
Leptospira do not multiply outside of a host and their survival depends on the environmental conditions in which they are found(2). Leptospira are susceptible to drying and pH changes can be detrimental. There is a higher incidence of Leptospirosis during the rainy season when there is an abundance of standing water and swampy conditions(3).
In an attempt to control the disease, vaccination programs have been instituted. In developed countries pigs, cattle and domestic dogs are widely vaccinated, however, the vaccine does not always contain relevant serovars. Human vaccines are widely applied in western countries, where risk of contagion is high(4).
Serologic testing is useful in diagnosing the disease. A four-fold rise in antibody titer to a Leptospira serovar is considered significant. It is not unusual to see elevated titers to multiple serovars due to cross-reactions(2). If there is a positive cross-reaction the serovars with the highest titers are considered to be most significant.
The Microscopic Agglutination Test (MAT) is the standard laboratory method to serologically diagnose Leptospirosis. Biogal’s ImmunoComb®, which is based on the “dot”-ELISA technology, is more sensitive than the MAT. The current ImmunoComb® Canine Leptospira test kit(5a) is suitable for evaluating antibody titers to the L. Canicola and L. Icterohaemorrhagiae serovars. Biogal has recently developed a kit(5b) with an expanded range of Lepto serovars. In addition to the two serovars mentioned above, the new kit tests for L. Grippotyphosa and L. Pomona serovars, which are most commonly found in wild animals in North America.
References
1) Noel R. (2002). An overview of canine leptospirosis. www.vet.uga.edu/vpp/clerk/noel/
2) McDonough, P.L. (2001). Leptospirosis in dogs-current status, Recent Advances in Canine Infectious Diseases. International Veterinary Information Services, July. www.ivis.org
3) Noyes, E. (2004). Coping with leptospirosis caused by serovars not in vaccine. VIN Message Boards, Oct.
4) Levett, P. Leptospirosis. (2001). Clinical Microbial Reviews, 14(2), 296-326.
5) a. ImmunoComb® Canine Leptospira Antibody Test Kit (50CLC201 for 12 tests / 50CLC210 for 120 tests)
b. ImmunoComb® Canine Tetra Leptospira Antibody Test Kit (50CLB201 for 12 tests / 50CLB210 for 120 tests)
Puppy Shots: Vaccination Issues for Breeders
By Christie Keith(1) (Abstract)
Most breeders are looking for a vaccination program that is as safe and effective as possible. Conventional vaccine protocols are designed to give multiple vaccinations to puppies a few weeks apart. Most people and even many veterinarians believe that more than one vaccine is needed to "prime" the immune system or build immunity. But, with modified live vaccines for canine distemper and parvovirus, this isn’t really necessary.
Vaccinations are repeated for two main reasons, habit and to catch those few individuals who for some reason do not respond to the first vaccination. A single immunizing dose of modified live vaccine - in other words, one vaccine that works - will form long term, probably lifetime immunity to canine distemper and parvovirus infection(2).
We don’t need to keep repeating the vaccines to know if they worked, either. Although titers as a measure of ongoing immunity may not be that useful, as a measure of whether or not an animal developed immunity from a recent vaccination, they are very reliable. Since it typically takes 7 - 10 days for immunity to form, if you test antibody titers ten days after vaccinating for distemper or parvo, you will know if the puppy had an immune response. You don’t have to guess.
If your puppy already seroconverted due to the vaccines that he or she was given, there is no reason or benefit to repeat them. The puppy is already immune and won’t get "more immune:" There is no "booster" effect, because the antibodies from the first vaccine will wipe out the vaccine virus, just like maternal antibodies do(3).
Some puppies will not form humoral immunity (seroconvert) from a vaccination. Most often this is due to the presence of maternal antibodies that they get from the colostrum in their mother’s milk. It is common for a pup to have enough maternal antibody to inactivate a parvovirus vaccination, but not enough to protect against the disease. Add that to the fact that maternal antibodies to parvovirus may be long lasting (up to 22 weeks), and you can see why many puppies that are vaccinated for parvo still come down with the disease.
Other causes for non-conversion to vaccination include improper vaccine shipping, storage, or handling, a low quality vaccine, or immune problems in the puppy. Most of time when a pup develops disease shortly after vaccination, it is not due to primary vaccination failure. It is a case of the animal not being immune at the time when it is exposed to the virulent virus.
The answer is not to vaccinate earlier and more frequently, but to vaccinate scientifically.
References
(1) Caber Feidh Scottish Deerhounds website; www.caberfeidh.com/PuppyVax.htm
(2) Ford, R. B. & Schultz, R. D. (2000). Vaccines and vaccinations: Issues for the 21st Century. Kirk’s Current Vet. Therapy, XIII.
(3) Schultz, P. & Schultz, R. D. (2000). Canine and Feline Vaccines. Kirk’s Current Vet. Therapy, XI.
Feline Panleucopenia – Part 1
By Ephraim Keren, VMD
This is a two-part article about feline Panleucopenia. This first part addresses clinical signs, diagnosis and treatment. The second part, which appears in the ImmunoComb® News issue #21, discusses the topics of vaccination and control.
Background
Feline Panleucopenia (FP) is a highly infectious disease affecting the domestic cat and other Felidae. The etiologic agent is a Parvovirus, which is closely related to canine Parvovirus. Infection is spread by direct contact with acutely infected animals or a contaminated environment. Transmission via recovered carriers has also been described.
The disease is characterised by a marked decrease in circulating white blood cells and destruction of the intestinal mucosa leading to enteritis. Young unvaccinated kittens are at greatest risk of infection, particularly when they lose their maternal antibody protection.
Clinical Signs
The severity of the disease varies from a mild transient fever and leucopenia, to a severe, peracute syndrome where the cat may be found dead. Subclinical infection is also known to occur.
Typical signs of FP include:
» Lethargy, anorexia, and apparent thirst but refusal to drink
» Vomiting
» Abdominal pain due to gas-filled intestines
» Diarrhea or dysentery leading to dehydration
» High mortality rate (25 to 75%)
Diagnosis
A presumptive diagnosis of feline Panleucopenia may be based on clinical signs, vaccination status, and a history of recent possible exposure. Several laboratory methods are used to confirm the diagnosis:
» Hematology (low white blood count-Panleucopenia).
» Identification of FP virus in the feces (kits for the detection of canine parvovirus antigen in feces may be used).
» A four-fold rise in antibody titer to FPV in acute and convalescent sera is diagnostic evidence of infection.
» In fatal cases, gross necropsy findings and histopathology of intestine, mesenteric lymph node and spleen are helpful.
Treatment
Supportive treatment of FP is aimed at maintaining hydration and balance of electrolytes and containing secondary bacterial infections in order to allow the cat’s impaired immune system to mount a defense. In addition to good nursing care, treatment regimens typically include:
» A parentral, bactericidal, broad-spectrum antibiotic such as amoxycillin and clavulanic acid or a cephalosporin.
» Subcutaneous or intravenous fluids: 5% dextrose saline, lactated Ringer’s solution or balanced electrolyte solutions.
» An anti-emetic, such as metoclopromide, may reduce fluid loss.
» Nutritional supplements when gastro-intestinal signs have diminished. Low doses of diazepam can be used just before feeding to stimulate appetite.
References
(1) www.provet.co.uk/infectiousdiseases
(2) Feline Panleucopenia, In The Merck Veterinary Manual, National Publishing Inc. Eighth edition.
From the Editor: Antibody testing in puppies
I received the following report from a pet owner who was looking into bringing a purebred puppy to Israel;
"I was "flabbergasted" to learn that a puppy must be vaccinated for rabies at least one month before entering the country." Since rabies vaccinations are not administered to pups younger than 3 months of age, this individual was saddened to learn that he would not be able to import a puppy younger than 4 months old.
Four months old is the age when most veterinarian’s conclude their series of "puppy shots" in accordance with the vaccine manufacturer’s label instructions. This practice, as discussed in Christie Keith’s article on page 3 in the issue of the IC News, is why veterinarians typically advise their clients to keep puppies under house quarantine until they are adequately immunized against canine distemper, hepatitis, parvovirus and leptospirosis.
Clearly, the puppy’s health is of primary concern. However, a prolonged period of isolation, which limits the pup’s opportunity for social interaction, may also have a negative impact upon its behavioral development(1). In both cases, the puppy would be better off if the number of vaccinations and waiting time after vaccination could be reduced while guaranteeing that puppy has adequate immunity to the various infectious diseases.
Whether we are talking about safeguarding public health, as with rabies vaccination requirements, or protecting a puppy against other diseases, current vaccination protocols do not pay attention to individual assessment to confirm whether or not the puppy is actually immune. The only way to determine if the puppy has mounted an adequate immune response is by serologic testing of the animal’s antibody levels.
Biogal’s ImmunoComb® test kit for determination of antibody levels to canine distemper and parvovirus offers the veterinarian an opportunity to evaluate the effectiveness of vaccinations that he or she gives. Perhaps of greater importance, this method can identify any animals that remain susceptible to infection because they have not responded immunologically, for whatever reason.
(1) Waner, T. (2003). Post-vaccination evaluation of the immunization status of puppies for canine parvo and distemper viruses using an in-clinic ELISA test. Israel Journal of Veterinary Medicine, 58(4), pp. 104-7.
Vet Forum: Epidemiology of FCoV - FIP
By Ephraim Keren, VMD
We received the following question from a cat owner in the U.S. regarding the epidemiology of FCoV - FIP.
Several months ago the female of my pair of cats died from FIP. At the time, the male was tested positive for FCoV antibodies which left me concerned about his health status. I would like to know if he still has antibodies to FCoV and is shedding the virus.
It is important for me to know if the male is infected with FCoV and may be a carrier before introducing anothe cat into the household. What do you suggest?
The Vet Forum replies:
It is important for you to understand that most cats infected by FCoV do not develop FIP. A positive antibody test means that your cat was exposed to the virus. Even if he is currently infected, antibodies in the blood do not necessarily indicate concurrent shedding of the virus. That can only be determined by testing the feces, not the blood.
The ImmunoComb® FCoV test determines antibody levels in the blood. If in a repeat test (3 months after the first test) the antibody titer is declining, the cat probably is not shedding FCoV. This also means that the cat is not a carrier and will not develop FIP. It would be safe then to introduce another cat into the house.
Before you bring home the new cat, it would be a good idea to test her for FCoV. If she is antibody negative for FCoV, it is safe to bring her home. If the new cat is antibody positive, you will run the risk of reinfecting your male. Hope this has been helpful.