Diagnosis of Borrelia‐associated uveitis in two horses

Borrelia burgdorferi, the etiologic agent of Lyme disease is a tick born spirochetal infection. Clinical signs of Lyme borreliosis are uncommon in horses, but when present they are often vague and nonspecific. In horses, Lyme borreliosis has been implicated in musculoskeletal, neurological, reproductive, and ocular disorders, including uveitis, but definitive diagnosis can be challenging as the causative agent is rarely isolated and serologic tests can be unreliable and do not confirm active disease. Here, we report two cases of equine uveitis associated with B. burgdorferi based on the identification of spirochetes within ocular fluids and confirmed with PCR testing. The two cases illustrate some of the challenges encountered in the recognition and diagnosis of equine Lyme borreliosis. Although only one of many possible causes of equine uveitis, Lyme disease should be considered a differential diagnosis, especially in endemic areas. Given the possibility for false negative results of serum tests during uveitis associated with B. burgdorferi and the failure of such tests to confirm active infection, a combination of cytologic assessment, antibody, and/or PCR testing of ocular fluids may be worthwhile if the clinical suspicion for Lyme uveitis is high.     

ACVIM small animal consensus statement on Lyme disease in dogs: diagnosis, treatment, and prevention

The purpose of this report is to offer a consensus opinion of ACVIM diplomates on the diagnosis, treatment, and prevention of Borrelia burgdorferi infections in dogs (canine Lyme disease). Clinical syndromes known to commonly be associated with canine Lyme disease include polyarthritis and glomerulopathy. Serological test results can be used to document exposure to B. burgdorferi but not prove illness. Although serum enzyme-linked immunosorbent assay/indirect fluorescent antibody assay titers can stay positive for months to years after treatment, quantitative C6 peptide antibody paired tests need more study. Serological screening of healthy dogs is controversial because it can lead to overdiagnosis or overtreatment of normal dogs, most of which never develop Lyme disease. However, serological screening can provide seroprevalence and sentinel data and stimulate owner education about tick infections and control. Although it is unknown whether treatment of seropositive healthy dogs is beneficial, the consensus is that seropositive dogs should be evaluated for proteinuria and other coinfections and tick control prescribed. Tick control can include a product that repels or protects against tick attachment, thereby helping to prevent transmission of coinfections as well as Borrelia spp. Seropositive dogs with clinical abnormalities thought to arise from Lyme disease generally are treated with doxycycline (10 mg/kg q24h for 1 month). Proteinuric dogs might need longer treatment as well as medications and diets for protein-losing nephropathy. The ACVIM diplomates believe the use of Lyme vaccines still is controversial and most do not administer them. It is the consensus opinion that additional research is needed to study predictors of illness, "Lyme nephropathy," and coinfections in Lyme endemic areas.     

Diagnostic aspects of Borrelia-infections in dogs

This paper discusses the problem of diagnosing borreliosis (Lyme disease) in dogs. A prospective cohort study in the Kempen district, a known Borrelia focus in The Netherlands, showed that dogs with the presumptive symptoms of borreliosis, episodic malaise and lameness, had significantly higher and longer lasting anti-Borrelia IgG titers than asymptomatic dogs. A small part of these dogs also had antibodies directed against the IR6 (C6) antigen which indicates persistent active Borrelia infection. A few typical case histories are presented. Dogs with episodic malaise and lameness with persistent high IgG titers are suspect of suffering from borreliosis. IR6 antibodies make this diagnosis likely. Initially, such patients should be treated with doxycyclin (10 mg/kg 1dd) for 10 days. If the symptoms recurr within a few months, a longer treatment (eg 6 weeks) should be considered. Bernese mountain dogs were strongly over-represented among the borreliosis patients in the cohort study and most high titered samples among those submitted for--diagnostic--serology appear to come from this breed, which suggests that these dogs have difficulties with clearing this tick-borne infection.     

Canines as sentinels for Lyme disease in San Diego County, California.

Prevalence of Lyme borreliosis in canine sentinels has been shown to correlate with infection in humans. One thousand canine sera (917 dogs, 83 coyotes) obtained from animal control authorities and area veterinarians were screened by ELISA for antibodies to Borrelia burgdorferi. Results were validated by Western blot and indirect fluorescent antibody (IFA) tests at referee laboratories. Criterion for a positive Western blot was presence of 5 of 10 of the most common antigen IgG bands; for IFA, >1:128 or the equivalent when correcting for interlaboratory variability. Twenty-two of 1,000 canines were confirmed serologically positive (21 dogs and 1 coyote; seroprevalence 2.3% and 1.2%, respectively). Lifestyle, breed size, gender, and age were not statistically predictive of seropositive status. No regional clustering of seropositive animals was detected. The low prevalence of seropositivity in sentinel canines suggests the Lyme borreliosis hazard in San Diego County is minimal.     

Canine borreliosis: a laboratory diagnostic trial

The aim of this study was to investigate samples from dogs suggestive of active canine borreliosis (group A) by culture and PCR and the detection of antibodies against Borrelia burgdorferi sensu lato in order to confirm a presumptive clinical diagnosis of canine borreliosis by laboratory results. Criteria for such a diagnosis were: history of tick exposure, lameness, neurological signs, nephropathy, lethargy, anorexia, and fever. A total of 302 samples comprising EDTA blood, urine, synovial fluid, cerebrospinal fluid, and tissue (skin, synovial membrane, kidney) from 98 dogs (26 with arthritis, 46 with neurological signs, 21 with nephropathy, 5 with non-specific symptoms) were collected and examined. Moreover, 55 healthy dogs (group B) and 236 dogs with symptoms or injuries unlikely to be associated with borreliosis (group C) were included in this study. Blood serum samples collected from all individuals (n=389) were analysed by ELISA. Twenty-one (21%) out of 98 dogs from group A, 4 (7%) out of 55 from group B and 15 (6%) out of 236 dogs from group C were positive for antibodies against B. burgdorferi sensu lato. The seroprevalences between groups A, B and C differed significantly. None of the corresponding samples investigated by PCR and culture were positive for spirochetal DNA or viable spirochetes. Borrelia afzelii was grown from one EDTA-blood sample but the corresponding blood serum sample remained antibody-negative. Consequently, the etiologic role of B. afzelii in this case is unclear. In approximately 40% of the presumptive canine borreliosis cases, other lesions have been found to be responsible for clinical signs. This study affirms that a definitive diagnosis of canine borreliosis cannot be made by clinical symptoms and serology based on a single consultation. Moreover, this study clearly revealed that the diagnostic sensitivity is enhanced by a thorough consideration and exclusion of other diseases.     

Canine haemobartonellosis, canine hepatozoonosis, and feline cytauxzoonosis

Although Lyme borreliosis (Lyme disease), ehrlichiosis, Rocky Mountain spotted fever, and babesiosis occur more frequently in dogs or cats, from a clinical standpoint, other tick-borne diseases such as canine haemobartonellosis, canine hepatozoonosis, and feline cytauxzoonosis are just as important to recognize. Information concerning these less common tick-borne diseases are discussed, including their causative agents and their relationship to disease pathogenesis, diagnosis, treatment, and prevention.     

Lyme borreliosis

Despite more than 25 years' experience with Lyme borreliosis, much remains to be learned about this complex zoonosis. Practicing veterinarians, particularly those in the northeastern and upper midwestern states, where Lyme borreliosis is highly endemic, should be familiar with the ecologic features and typical clinical signs of Lyme borreliosis. Interpretation of signs and serologic test results should be made with consideration of the regional prevalence of Lyme borreliosis and the animal's opportunity for exposure to infected Ixodes spp. The availability of recently marketed topical acaracides is a valuable adjunctive measure in prevention of Lyme borreliosis. A maximally effective prevention strategy should include consideration of environmental modification, activity restrictions, routine examinations for ticks, prompt removal of attached ticks, and vaccination. Technologic advances, such as the C6 EIA and the Osp A recombinant vaccine, offer the promise of additional tools for the clinical management and prevention of this tick-borne zoonosis.     

Western immunoblot analysis for distinguishing vaccination and infection status with Borrelia burgdorferi (Lyme disease) in dogs.

Serodiagnosis of Lyme borreliosis in dogs is complicated by the use of commercially available Lyme disease vaccines that may cross-react with certain diagnostic assays. Western immunoblotting may be used to distinguish between dogs naturally exposed and those vaccinated against Borrelia burgdorferi. Because current vaccines are not 100% efficacious and dogs may be vaccinated after natural exposure, certain dogs may show serum antibody responses against both natural and vaccine exposure (dual status). In this study, samples from 17 nonexposed, 17 B. burgdorferi-bacterin vaccinated, 13 naturally exposed, and 8 dual-status dogs were tested by western immunoblot to determine if dual-status dogs could be reliably differentiated from naturally infected or vaccinated dogs. Reaction to outer surface protein A antigen of B. burgdorferi (31 kD) was a consistent marker for vaccination, appearing in all samples from vaccinate and dual-status dogs and in no samples from single-status naturally exposed dogs. Antibodies to 4 bands, at 80, 39, 29, and 28 kD, were present in all naturally infected and dual-status dogs. No samples from vaccinated or nonexposed dogs were reactive to all 4 of these bands simultaneously. Thus, vaccine and natural exposure produce differing antibody responses, whereas dual-status dogs produced the full antibody response of both types of exposure.     

Canine borreliosis.

A guild of organisms carried by the same vector (Ixodes ticks) in Lyme-endemic areas may be confounding the understanding of Lyme disease in dogs. A new diagnostic method, the C6 peptide test for Lyme, and serology and PCR testing for Ehrlichia, Babesia, and Bartonella species will help to sort out seroprevalence and symptomatology caused by exposure to these agents or by coinfections. In addition, Rickettsia, Leptospira, Mycoplasma species, and more could be involved in dogs diagnosed with a "doxycycline-responsive" disease. The author does not recommend treating asymptomatic Borrelia carrier dogs, but does recommend screening them for proteinuria and for exposure to other agents. A positive Lyme titer is a marker of exposure to Ixodes ticks and the agents they carry. The risk/benefit of vaccination will be understood better as the symptomatology and immunopathogenesis of Lyme disease are defined. Meanwhile, tick control is highly recommended for all dogs in Lyme-endemic areas.     

Asymptomatic leptospiral infection is associated with canine chronic kidney disease

Canine leptospirosis is characterized by an acute or chronic disease. Some dogs may act as asymptomatic carriers, keeping the agent in the renal tubules and eliminating it in the urine for an extended period. Chronic kidney disease (CKD) is multifactorial and pathophysiology has been widely discussed. The aim of the study was to investigate whether the occurrence of CKD may possibly be associated with asymptomatic leptospiral infection in dogs in endemic regions. Serology and urine PCR were performed in 16 dogs with CKD and 48 healthy dogs from an endemic area. Dogs with CKD were more frequently shedders (75%) than non-CKD animals (20.8%). Therefore, our results demonstrate that asymptomatic leptospiral infection is associated with canine chronic kidney disease and that differential diagnosis is important for dogs from endemic areas presenting CKD. The early detection of shedders, besides the obvious impact on Public health may also help to improve the animal health and avoid the development of CKD.     

Intradermal and serological testing for mites in healthy beagle dogs

Background – Intradermal testing (IDT) is widely used in veterinary medicine to select allergens for immunotherapy. The recommended concentration for mites is 250 protein nitrogen units (PNU)/mL. It is not known whether healthy dogs responding to this concentration have asymptomatic sensitization or irritation. Furthermore, interbatch and intersupplier variability of allergens has not been fully addressed. Hypothesis/Objectives – The incidence of positive IDTs in healthy beagles was recorded and the value of combining these results with serology to differentiate between asymptomatic sensitization and irritancy evaluated. Additionally, the interbatch and intersupplier variability of allergens was assessed. Animals – Seventeen healthy laboratory beagles with no history or clinical signs of canine atopic dermatitis were used. Methods – Intradermal tests were performed with four mite allergens from two suppliers (varying batches). An initial IDT at 250 PNU/mL was used to determine whether decreasing or increasing test concentrations were used in the subsequent titration IDTs. Additionally, two IgE ELISA tests from different manufacturers were performed. Results – Seven of 17 dogs showed IDT reactions at 250 PNU/mL. There were highly significant allergen interbatch and significant intersupplier correlations and agreement. The associations between the IDT reactions and the IgE serologies statistically identified two groups of dogs: one with positive serology and IDT reactions at 250 PNU/mL; and another with negative serology and IDT reactions. Conclusions and clinical importance – Our results suggest that dogs that have IDT reactions and positive serology are asymptomatically sensitized, while dogs that react at higher allergen concentrations, but have negative serology, do so as a result of irritant reactions.     

Clinical and serologic studies of canine borreliosis

During 1984 and 1985, blood samples were obtained from 271 dogs that were suspected of having borreliosis. The dogs lived in areas known to be infested with ticks and had been examined because of limb/joint disorders or for unknown illnesses marked by fever, anorexia, or fatigue. Lameness had been the most frequently reported clinical manifestation. Analyses of serum specimens, by an indirect fluorescent antibody (IFA) method or by an ELISA, detected antibodies to Borrelia burgdorferi, the etiologic agent of borreliosis in dogs and of Lyme disease in human beings. Antibody to B burgdorferi was detected in 76.3% of 114 specimens from dogs living in the lower Hudson Valley region of New York State (predominantly Westchester County), in 66.5% of 155 specimens from dogs from southern Connecticut, and in single specimens from dogs from Rhode Island and California. Geometric mean antibody titers peaked during the winter. Results of IFA tests and ELISA were in agreement, but the latter method yielded less variable results, had greater sensitivity, and was more easily standardized. Five dogs from New York State and Connecticut seropositive to B burgdorferi had developed kidney disorders during or after episodes of intermittent lameness. Application of murine monoclonal antibody in an IFA procedure verified the presence of B burgdorferi in renal cortical tissues from one dog.     

The prevalence of antibodies against B. burgdorferi, an indicator for Lyme borreliosis in dogs? A comparison of serological tests

Five serological tests for the detection of IgM and IgG antibodies to Borrelia burgdorferi, the causative microorganism of Lyme borreliosis (LB), were compared in 1177 sera from Dutch dogs: 401 healthy working hunting dogs, 100 healthy city pet dogs, 629 city dogs suspected of having LB with various clinical symptoms, and 47 hunting dogs with intermittent lameness. The results of the in-house species-independent enzyme immunoassay (i.e. an EIA which can be used to test serum samples from different animal species) showed a strong agreement (kappa: 0.78-0.81) with those of an experimental and a commercially available EIA (Genzyme Virotech, Rüsselsheim, Germany) for the detection of canine IgG antibodies to B. burgdorferi. Furthermore, the sensitivity of the in-house EIAs for the detection of antibodies to B. burgdorferi was independent of the antigenic heterogeneity, as demonstrated by the results of sera from dogs suspected of LB with various clinical symptoms: lameness (n = 60), and neurological (n = 60) and skin disorders (n = 52). Because of its high sensitivity for IgM antibodies, the indirect assay (Diagast, Pessac, France) proved to be an interesting tool for the detection of an acute Lyme infection in dogs. However, in this study a positive serological result could not be linked to any clinical symptom that has been related to LB in dogs. Results showed no difference in seroprevalence between dogs considered at high or at low risk of a B. burgdorferi infection. It was concluded that LB is an uncommon disease in the Dutch dog population despite the fact that many of Dutch dogs are infected with B. burgdorferi. Because of this low prevalence, the use of any immunoassay to support the clinical diagnosis of LB in dogs might be of limited value. Nevertheless, the species-independent EIA could be valuable in seroepidemiological studies when sera of several different animal species need to be tested.     

Infectivity of seropositive dogs, showing different clinical forms of leishmaniasis, to Lutzomyia longipalpis phlebotomine sand flies

Visceral leishmaniasis (VL) is a growing zoonosis with an increasing number of new cases and a rapid geographical spreading of the disease. In the present study, a canine survey was carried out in the city of Montes Claros (320,000 inhabitants), an endemic area of American visceral leishmaniasis in the state of Minas Gerais, Brazil. A total number of 4795 dogs were examined by serology, which showed a rate of seropositivity of 5%. Isoenzymatic analysis confirmed Leishmania infantum chagasi as the local aetiological agent of CVL. Canine tissues were assayed for the presence of Leishmania parasite DNA using different techniques. The infectivity of asymptomatic, oligosymptomatic and symptomatic seropositive dogs was tested by xenodiagnosis using laboratory reared Lutzomyia longipalpis. Rates of infection of 5.4%, 5.1% and 28.4% were found for the phlebotomine sand flies that fed in asymptomatic, oligosymptomatic and symptomatic dogs, respectively. Our results indicate that, under experimental conditions, symptomatic dogs are about four times more infective to VL vectors than oligosymptomatic or asymptomatic animals. The lower infectivity rates of dogs displaying any of the last two clinical forms of leishmaniasis, however, must be taken into account in the epidemiology of CVL.     

Serological studies on the infection of dogs in Ontario with Borrelia burgdorferi, the etiological agent of Lyme disease

A serological study was undertaken to determine whether dogs in Ontario are being exposed to Borrelia burgdorferi, the etiological agent of Lyme disease. This study consisted of a survey of randomly selected dogs and testing of diagnostic submissions from candidate Lyme disease cases. The survey of 1,095 dogs, bled between January 1988 and August 1989, revealed a total of 65 (5.9%) enzyme-linked immunosorbent assay (ELISA) reactors, of which 22 had immuno-fluorescent antibody assay (IFA) titers ≥1:32. All but one of the IFA-positive and 10 of the ELISA-positive, IFA-negative sera were further tested by western blot. Eight western blot positive and three equivocal reactors were obtained. Three of the eight confirmed reactors had visited areas known to be endemic for Lyme disease, leaving five reactors that might have been infected in previously undocumented areas for B. burgdorferi activity in Ontario. Diagnostic submissions of sera from 223 dogs were received between August 1987 and February 1992. Test results revealed 21 (9.4%) IFA reactors, of which only six had significant titers (≥1:256) and were reactive by an immunodot Borrelia test. All six dogs had travelled to known Lyme endemic areas. Based on results obtained from this study, it seems likely that the agent of Lyme disease is not widespread in Ontario.     

Feline heartworm disease: a clinical review

Feline heartworm disease is caused by the filarial nematode Dirofilaria immitis, and is transmitted by mosquitoes in heartworm-endemic areas worldwide. While dogs are the definitive hosts for this parasite, cats can also be infected, and the overall prevalence in cats is between 5% and 10% of that in dogs in any given area. The spectrum of feline presentations varies from asymptomatic infections to chronic respiratory signs, sometimes accompanied by chronic vomiting to acute death with no premonitory signs. Ante-mortem diagnosis can be challenging and relies on a combination of tests, including antigen and antibody serology, thoracic radiography and echocardiography. As treatment with heartworm adulticidal drugs can be life-threatening and heartworm infection in cats is often self-limiting, infected cats are frequently managed with supportive treatment (corticosteroids, bronchodilators, and anti-emetics). Surgical removal of filariae using extraction devices may be considered in some acute cases where immediate curative treatment is necessary, but filarial breakage during the procedure may result in an acute fatal shock-like reaction. Necropsy findings are mainly pulmonary and include muscular hypertrophy of the pulmonary arteries and arterioles on histopathology. A number of safe and effective macrocytic lactone drugs are available for prophylaxis in cats. These drugs can kill a range of larval and adult life-cycle stage heartworms, which may be advantageous in cases of owner compliance failure or when heartworm infection status is undetermined at the time prophylaxis is commenced. An index of suspicion for feline heartworm disease is warranted in unprotected cats with respiratory signs, and perhaps chronic vomiting, in areas where canine heartworm disease is endemic. Many cats, once diagnosed and with appropriate supportive care and monitoring, will resolve their infection and be free of clinical signs.     

Microalbuminuria and comparison of serologic testing for exposure to Borrelia burgdorferi in nonclinical Labrador and Golden Retrievers.

Canine Lyme disease is caused by the spirochete Borrelia burgdorferi after transmission by an Ixodes tick, typically resulting in joint pain, fever and lethargy. Lyme nephritis is a poorly characterized syndrome associated with severe glomerular and tubular renal injury and poor clinical outcome in young to middle-aged dogs positive for exposure to B. burgdorferi. The aims of this study were to identify associations between natural exposure to B. burgdorferi and the presence of microalbuminuria in nonclinical young Labrador and Golden Retrievers and to compare two commonly used serologic tests available to document B. burgdorferi exposure: the Western blot and the commercial point-of-care C6 peptide enzyme-linked immunosorbent assay (ELISA) tests. Microalbuminuria was assessed using a commercial point-of-care ELISA specific for canine albumin. Blood and urine samples from 268 asymptomatic Labrador and Golden Retrievers were included. Of these, 18.7% were positive for B. burgdorferi exposure according to the C6 ELISA; 21.2% were positive for natural exposure to B. burgdorferi and 11.5% for vaccinal antibodies according to the Western blot. The agreement rate was 93% between the two tests (kappa = 0.78, P < 0.0001) for natural exposure. Urine from 6.1% of the dogs was positive for microalbuminuria. There was no association between microalbuminuria and exposure to B. burgdorferi based on results of a Western blot (P = 0.57) or C6 ELISA (P = 0.53). Microalbuminuria is likely not a consequence of B. burgdorferi exposure in young nonclinical Labrador and Golden Retrievers.     

Serological testing—An alternative to boosters?

The issue of the duration of immunity, particularly for the modified live viral components of veterinary vaccines, has been a significant part of the recent vaccination debate. One manufacturer has increased the recommended booster interval for these components to 3 years give name and another now states 'up to 4 years' immunity. There remain many unanswered questions regarding this duration of immunity (DOI). Studies suitable for data sheet claims are time consuming and costly and can only be performed in laboratory dogs under tightly controlled conditions. Evidence from rabies serology testing in the UK shows that the response of individual animals to routine vaccination is highly variable. Much of the published field evidence on the persistence of antibody titres originates from North America, where vaccination strategies and reservoir species differ from Europe. Quantifying the effect of exposure to field virus on the maintenance of immunity in these studies is impossible, and little is known of the circulation of virus in unvaccinated dogs and wild mammals throughout Europe. If owners or vets are concerned about revaccination one option is to assess the need for each booster by performing a blood test. There is some published evidence of the relationship between antibody titres and protective immunity, and tests are available to measure responses to individual viral components of the routine canine and feline vaccines. It must be remembered that most commercial tests to assess immunity only measure antibodies, which are only one aspect of the immune response to vaccination. It is therefore possible that animals without or with low antibody titres are in fact protected. Serological tests are an option if owners are unwilling to have their animal boostered without evidence that it is needed. However, the cost of these tests is likely to exceed that of booster vaccination for the foreseeable future.