Diagnostic Services Laboratory, Atlantic Veterinary College University of Prince Edward Island 550 University Avenue, Charlottetown PE, C1A 4P3 Phone: 902.566.0860 • Fax: 902.566.0723 • www.upei.ca/diagserv/ Diagnostic Update Serologic Testing for Lyme Disease February 2009, Volume 3, Issue 1 in Dogs By Barbara Horney, Veterinary Clinical Pathologist In this Issue: Lyme disease is associated with Borrelia Lyme disease testing in dogs ............... 1 burgdorferi (Bb) infection, usually through a tick bite, and can be considered to be an Strongyloides stercoralis infection ..... 2 emerging disease in the Atlantic Canada region. The Ixodes scapularis ticks that carry this agent Therapeutic drug monitoring .............. 3 appear in our region either by expansion of their geographic range or by being carried from Finch population mortalities ............... 5 endemic areas on migrating birds. In general, the proportion of dogs showing serologic Packing and shipping samples ............ 5 evidence of exposure to Bb in our region is low (less than 5%). Laboratory news .................................. 7 The following information and Staff focus ........................................... 8 recommendations on testing for Lyme disease have been adapted from the 2006 ACVIM Small Animal Consensus Statement on Lyme Disease in Dogs.1 1. Evidence of exposure to Bb (usually by demonstration of serum antibodies to Bb), 2. Clinical findings consistent with Lyme In endemic areas, 95% of dogs exposed to Bb disease which include: fever, arthropathy remain asymptomatic. The clinical signs of (lameness), nephropathy (proteinuria), Lyme disease are relatively nonspecific and may 3. Consideration of other differentials, and be similar to those associated with other 4. Response to treatment. infectious and noninfectious agents. The consensus statement maintains that diagnosis of canine Lyme disease cannot be made from an individual test and that presumptive diagnosis of Types of tests for antibody to Bb available: ELISA and IFA tests Lyme disease should include: : Identify serum antibodies to Borrelia but require Western blot testing to help Test Sample Testing Cost differentiate between a true positive and a required location (2008) vaccine response or infection with other Borrelia species. IDEXX 1 ml AVC $30.00 SNAP-4Dx†* serum IDEXX SNAP-4Dx (3Dx): Includes a IFA§ 1 ml Michigan $65.00 qualitative test for antibody to the C6 antigen serum (Sent though (expressed when a dog is infected with Bb and AVC) not present in the vaccine). A positive test indicates exposure to the Bb organism but does †In cases in which Lyme disease is the most likely not prove clinical disease. The antibody diagnosis and antibiotic therapy is instituted, a C6 response to the Lyme vaccine should not be quantitative test pre- and post- therapy may help to detected as a positive result by this method. A evaluate response to treatment. This test can be quantitative C6 antibody test is also offered requested through AVC (forwarded to an IDEXX through IDEXX which can be used to laboratory - please call AVC DS for cost) * demonstrate decreasing antibody levels after The 4Dx assay also includes tests for Anaplasma therapy. phagocytophilum, Erhlichia canis and Heartworm. §Followup testing of an IFA positive result by Western For patients with suspicious clinical signs: blot analysis (forwarded to Cornell for analysis) is Either testing type is valid. A positive result can recommended to differentiate from response to a vaccine support (but does not confirm) a diagnosis of or other Borrelia species. Lyme disease, as long as other possible causes of the clinical signs have been ruled out. References: Demonstration of rising titres (acute and 1. Littmen M, et al. ACVIM small animal consensus “convalescent” samples) are not required as the statement on Lyme disease in dogs: diagnosis, treatment clinical signs of Lyme disease usually develop and prevention. J Vet Intern Med. 2006;20:422-434. after seroconversion. In seropositive dogs, the C6 quantitative test can be useful to identify 2. Peregrine A, et al. Screening dogs in Ontario for decreasing antibody levels as a response to Borrelia burgdorferi and Ehrlichia canis should be therapy, with serum samples taken before and 6 selective rather than routine. Can Vet J. 2007;48:673. months post treatment. The consensus statement also recommends testing seropositive dogs for proteinuria which can be associated Strongyloides stercoralis infection in a with Lyme nephropathy. puppy Testing healthy dogs: By Gary Conboy, Veterinary Parasitologist This is somewhat controversial1 but it is generally not recommended in areas with a low A fecal sample was submitted for examination from prevalence of exposure to Bb, as the proportion a 3.5 month-old, male Yorkshire terrier with of false positives can be high even with a clinical signs of a cough and diarrhea. The dog had sensitive and specific test.2 been purchased and transported from western Canada to Prince Edward Island (PEI) 1.5 months Testing through the Atlantic Veterinary earlier. The dog had been treated with Interceptor College Diagnostic Services (AVC DS): (milbemycin oxime) for presumed lungworm When submitting a canine serum to test for infection due to a persistent cough that occurred antibodies to Bb, please specify which test you would like: 2 4 weeks after arriving on PEI. The cough improved with deworming. The puppy then developed diarrhea, was positive for Giardia canis cysts on fecal flotation and was treated with a 5 day course of fenbendazole at 50 mg/kg. After a short period of clinical improvement, the cough and diarrhea returned and progressively worsened. A second fecal sample was submitted for flotation and Baermann examination. The flotation was still positive for Giardia canis cysts and the Baermann detected first-stage larvae of Strongyloides stercoralis (Figures 1 & 2). The puppy was treated with ivermectin (0.2 mg/kg SQ) and showed marked improvement, with Figure 2: Anterior-end of first-stage larvae of clinical signs resolving over the next 7 days. Strongyloides stercoralis larvae showing Post-treatment Baermann fecal examinations characteristic esophagus. were negative. known whether the dog acquired the infection in western Canada or PEI. The prevalence of Giardia infection in puppies is high (up to 40%) and infection can result in diarrhea, but most infections are subclinical. The presence of Giardia in this dog was likely incidental. This is the second case of S. stercoralis we have diagnosed in a dog with clinical signs involving chronic cough. Fenbendazole and ivermectin have both been recommended for use in the treatment of dogs infected with this parasite. However, the 5 day course of fenbendazole given for the Giardia did not result in a cure. Strongyloides stercoralis is a serious pathogen in humans which heightens the importance of proper diagnosis, treatment and diagnostic post-treatment follow-up Figure 1: Iodine stained first-stage larvae of in cases involving dogs or cats. Strongyloides stercoralis recovered by Baermann fecal examination from a puppy with The Therapeutic Drug Monitoring of clinical signs of a cough and diarrhea. Phenobarbital Strongyloides stercoralis infects the small By Sandra McConkey, Veterinary Clinical Pathologist and intestine of dogs and cats and can cause a Pharmacologist life threatening enteritis with clinical signs of diarrhea. Animals acquire infection by the Therapeutic drug monitoring (TDM) is the ingestion or direct skin penetration of infective measurement of the plasma or serum drug third-stage larvae. Larvae of S. stercoralis concentrations in patients to determine if the undergo migration through the lungs during dosage is correct. It is typically used for drugs their developmental cycle, and this was the with a narrow therapeutic index or variable cause of the cough in this patient. Strongyloides pharmacokinetics. Diagnostic Services at the stercoralis occurs worldwide and it is not 3 Atlantic Veterinary College does TDM for more Phenobarbital treatment can be associated with than 150 clients every month. The majority of several adverse effects, including sedation, samples are evaluated for phenobarbital and polyuria, polydipsia, polyphagia and behavioral potassium bromide (KBr) concentrations with changes. Many animals experience one or more lower numbers of samples submitted for of these signs during the first few weeks of digoxin, theophylline, gentamicin and treatment, but these usually spontaneously resolve cyclosporine. Uncommon drugs can be with the development of pharmacokinetic and evaluated by special request. pharmacodynamic tolerance. Occasional animals will continue to demonstrate these signs despite Phenobarbital has both a narrow therapeutic blood phenobarbital concentrations in the desired index and a variable half-life. In fact, the therapeutic range. These dogs should be changed therapeutic response to phenobarbital to alternative anti-convulsants. corresponds better with its serum concentration than its dosage. Most dogs require a Mild elevations of ALT activity and mild to phenobarbital concentration within a therapeutic marked elevations of ALP activity can occur in range of 54-190 µmol/L for sufficient seizure animals on chronic phenobarbital therapy. These control. The wide range allows for several changes are believed to be due to phenobarbital upward adjustments of the dosage over time if induction rather than secondary to a toxic control is lost. The addition of a second reaction.