Anaplasma phagocytophilum infection in a dog: identifying the causative agent using PCR

Prevalence of subclinical infectious agents in a blood donor population tested on every donation

OBJECTIVES

This study aimed to assess the prevalence of blood-borne infectious agents in healthy, client-owned dogs from a blood donor population in Portugal and Spain, and to address the importance of a screening protocol on every donation.

MATERIALS AND METHODS

Client-owned healthy dogs were tested before each donation on a veterinary blood bank. Blood samples from new potential donors, and from regular donors, were tested by real-time polymerase chain reaction for Leishmania species, Ehrlichia species, Brucella species, Babesia species and Anaplasma species Serological tests were also performed for Leishmania species, Ehrlichia species and Dirofilaria immitis. All donors were tested for every infectious agent in each donation.

RESULTS

The study found that out of a total of 8036 donors and 35,120 samples tested, 3.9% of blood donors tested positive for at least one of the agents, with the most prevalent being Anaplasma species (2.1%). Serological tests also revealed positive results in 14.0% of donors, with the highest percentage for Leishmania species (7.7%). Moreover, the study found that 28.2% of positive results were from dogs with negative results in donations performed 3 to 12 months before, and 18.0% of positive results were recent infections.

CLINICAL SIGNIFICANCE

These findings indicate a high prevalence of infectious agents in seemingly healthy, selected dogs eligible to become blood donors in the Iberian Peninsula, highlighting the importance of regular testing on every donation. This study emphasises the importance of a regular screening protocol for every donation instead of annual testing, as is commonly performed in veterinary medicine.

In-House-Diagnose der kaninen Anaplasmose unter Berücksichtigung von hämatologischen Veränderungen und der Beurteilung eines gefärbten Blutausstrichs

Gegenstand und Ziel: Im Rahmen der Diagnostik der kaninen Anaplasmose in der Tierarztpraxis sollen Abweichungen hämatologischer Parameter, die Beurteilung eines Blutausstriches und die Berücksichtigung der saisonalen Bedingungen zur Diagnose einer Anaplasmose führen. Material und Methode: Es wurden 57 Blutproben von Hunden untersucht. Die Diagnose einer kaninen Anaplasmose wurde durch Untersuchung eines gefärbten Blutausstriches in allen 57 Fällen bestätigt. Ergebnisse: Bei 56 Hunden (98,2%) wurde eine Thrombozytopenie nachgewiesen. Die Erythrozytenanzahl lag in 38,6%, der Hämatokrit in 24,5% und der Hämoglobinwert in 26,3% der Fälle unterhalb des Referenzbereichs. Mittels Retikulozytenzählung wurde in 78,6% der Fälle eine nicht regenerative Anämie diagnostiziert. Eine Leukopenie ergab sich zu 35,1%, eine Lymphopenie zu 66,7%, eine Neutropenie zu 10,9%, eine Monozytose zu 5,7% und eine Eosinophilie zu 15,4%. Schlussfolgerung: Die Resultate zeigen, dass bei Hunden die Verdachtsdiagnose einer Anaplasmose aufgrund von typischen hämatologischen Veränderungen gestellt werden kann. Die wichtigsten Veränderungen im Blutbild der betroffenen Hunde waren eine Thrombozytopenie, eine Lymphopenie und im Fall einer vorliegenden Anämie in den meisten Fällen eine nicht regenerative Anämie.

Granulocytic anaplasmosis in 63 dogs: clinical signs, laboratory results, therapy and course of disease

OBJECTIVES

To describe the clinical signs, laboratory results, therapy and course of disease in dogs with canine granulocytic anaplasmosis in which co-infections had been excluded.

METHODS

Medical records of dogs naturally infected with Anaplasma phagocytophilum were retrospectively evaluated with regard to clinical signs and laboratory abnormalities at the time of presentation, therapy and course of disease.

RESULTS

Nine hundred and seventy-four dogs with clinical signs suspicious for canine granulocytic anaplasmosis were tested for A. phagocytophilum DNA by modified real-time PCR; 72 dogs had a positive result. Nine of the positive dogs were excluded from further evaluation due to other diseases or lack of data. The most common clinical signs in the 63 A. phagocytophilum-positive dogs included in the study were lethargy and reduced activity (83%), fever (67%) and inappetence (63%). Thrombocytopenia was the most common laboratory abnormality (86%), followed by increased liver enzyme activities and hyperbilirubinaemia (77%), anaemia (70%), hypoalbuminaemia (62%) and leucocytosis (27%). Of 36 thrombocytopenic dogs tested for platelet-bound antibodies, 44% were positive. Of the 63 infected dogs, 59 (97%) recovered, two dogs died (epileptic seizures and immune-mediated haemolytic anaemia) and two were lost to follow-up.

CLINICAL SIGNIFICANCE

In areas where it is endemic, canine granulocytic anaplasmosis should be considered as a potential cause of acute nonspecific clinical signs or immune-mediated disease if tick exposure cannot be excluded.

Serologic responses to peptides of Anaplasma phagocytophilum and Borrelia burgdorferi in dogs infested with wild-caught Ixodes scapularis

Anaplasma phagocytophilum and Borrelia burgdorferi are both transmitted by Ixodes spp. and are associated with clinical illness in some infected dogs. This study evaluated canine antibody responses to the A. phagocytophilum p44 peptides APH-1 and APH-4 as well as the B. burgdorferi C6 peptide before and after doxycycline treatment. A total of eight dogs were infested with wild-caught I. scapularis for 1 week. Blood was collected prior to tick attachment and from Days 3-77 to 218-302 with doxycycline treatment beginning on Day 218. Blood was assayed for A. phagocytophilum DNA by PCR assay. Sera was assessed for antibodies by immunofluorescent antibody (IFA) test and ELISA. Anaplasma phagocytophilum DNA was amplified from blood of all dogs by Day 7. Antibodies to APH-4 were detected in serum as early as 14days after tick exposure and six dogs had APH-4 antibodies detected 3-7 days before antibodies against APH-1. All dogs were seropositive for A. phagocytophilum from Days 218 to 302. Antibodies to B. burgdorferi were detected in 6/8 dogs beginning 21days after I. scapularis infestation. Among the five dogs that remained seropositive at Day 218, C6 antibody levels declined on average 81% within 84days of initiating treatment. The results suggest that the APH-4 peptide may be more useful than APH-1 for detecting antibodies earlier in the course of an A. phagocytophilum infection. After doxycycline administration, C6 antibody levels but not APH-1 or APH-4 antibody levels decreased, suggesting a treatment effect on C6 antibody production.

Detection of antibodies against Anaplasma phagocytophilum in dogs using an automated fluorescence based system

Infection with Anaplasma phagocytophilum can cause significant illness in some dogs and accurate diagnostic assays are needed. The objectives of the study were to optimize an automated fluorescence system for the detection of antibodies against A. phagocytophilum in canine serum. Serum and blood was collected temporally from seven dogs inoculated parenterally with culture-derived A. phagocytophilum and from 36 dogs exposed to wild-caught, adult Ixodes scapularis for 7 days. The system was optimized using the samples from the parenterally inoculated dogs. The ability to detect antibodies against A. phagocytophilum in the I. scapularis exposed dogs by the automated system was compared with a diagnostic kit (ELISA) and an indirect fluorescent antibody assay (IFA). Each blood sample was also assayed for A. phagocytophilum DNA by polymerase chain reaction (PCR). Of the 36 dogs exposed to I. scapularis, A. phagocytophilum DNA was amplified from blood from 22 dogs by PCR with first positive results occurring on weeks 1 (seven dogs), 2 (nine dogs), 3 (four dogs), 4 (one dog), or 5 (one dog). PCR results were positive prior to detection of antibodies in any of the three antibody assays for 19 dogs. The automated fluorescence system and IFA detected antibodies against A. phagocytophilum earlier than the ELISA. In conclusion, A. phagocytophilum PCR assays on blood are indicated in dogs with suspected acute anaplasmosis if serum antibody assays are negative.

Molecular epidemiology of the emerging zoonosis agent Anaplasma phagocytophilum (Foggie, 1949) in dogs and ixodid ticks in Brazil

BACKGROUND

Anaplasma phagocytophilum is an emerging pathogen of humans, dogs and other animals, and it is transmitted by ixodid ticks. The objective of the current study was a) detect A. phagocytophilum in dogs and ixodid ticks using real-time Polymerase Chain Reaction (qPCR); and b) Determine important variables associated to host, environment and potential tick vectors that are related to the presence of A. phagocytophilum in dogs domiciled in Rio de Janeiro, Brazil.

METHODS

We tested blood samples from 398 dogs and samples from 235 ticks, including 194 Rhipicephalus sanguineus sensu lato, 15 Amblyomma cajennense, 8 Amblyomma ovale and 18 pools of Amblyomma sp. nymphs. A semi-structured questionnaire was applied by interviewing each dog owner. Deoxyribonucleic acid obtained from ticks and dog buffy coat samples were amplified by qPCR (msp2 gene). The sequencing of 16S rRNA and groESL heat shock operon genes and a phylogenetic analysis was performed. The multiple logistic regression model was created as a function of testing positive dogs for A. phagocytophilum.

RESULTS

Among the 398 blood samples from dogs, 6.03% were positive for A. phagocytophilum. Anaplasma phagocytophilum was detected in one A. cajennense female tick and in five R. sanguineus sensu lato ticks (four males and one female). The partial sequences of the 16S rRNA, and groESL genes obtained were highly similar to strains of A. phagocytophilum isolated from wild birds from Brazil and human pathogenic strains. The tick species collected in positive dogs were R. sanguineus sensu lato and A. cajennense, with A.cajennense being predominant. Tick infestation history (OR = 2.86, CI = 1.98-14.87), dog size (OR = 2.41, IC: 1.51-12.67), the access to forest areas (OR = 3:51, CI: 1.52-16.32), hygiene conditions of the environment in which the dogs lived (OR = 4.35, CI: 1.86-18.63) and Amblyomma sp. infestation (OR = 6.12; CI: 2.11-28.15) were associated with A. phagocytophilum infection in dogs.

CONCLUSIONS

This is the first report of A. phagocytophilum in ixodid ticks from Brazil. The detection of A. phagocitophylum in A. cajennense, an aggressive feeder on a wide variety of hosts, including humans, is considered a public health concern.

Acute granulocytic anaplasmosis in a captive timber wolf (Canis lupus occidentalis)

A 2-yr-old male captive timber wolf, kept in an outdoor enclosure in Austria, presented with anorexia, depression, and fever in June. Tick infestation was reported despite monthly acaricidal treatment. The microscopic examination of a blood smear revealed elementary bodies and morulae suspicious for Anaplasma phagocytophilum. Polymerase chain reaction confirmed the infection by the G-variant of the pathogen, also found in horses and humans but not in wild ruminants. The wolf seroconverted within 2 wk, and antibodies persisted thereafter. Therapy was started with doxycycline for 10 days, and the wolf recovered within 24 hr. Clinical symptoms and temporary changes in blood parameters (thrombocytopenia, lymphopenia, mild anemia) in this wolf show high similarity to granulocytic anaplasmosis seen in dogs. This is the first report on granulocytic anaplasmosis in a wolf, indicating that A. phagocytophilum might cause clinical disease in the wolf.

Association between Anaplasma phagocytophilum seroprevalence in dogs and distribution of Ixodes ricinus and Ixodes persulcatus ticks in Latvia

Anaplasma phagocytophilum has been detected in ticks in Latvia; however, this is the first study to investigate this pathogen in dogs in Latvia. The aims of this study were: (i) to determine A. phagocytophilum seroprevalence in dogs, (ii) to correlate A. phagocytophilum seroprevalence in dogs with the geographic distribution of the tick species Ixodes ricinus and Ixodes persulcatus, and (iii) to determine if seroprevalence for A. phagocytophilum is higher in dogs with clinical signs suggestive of canine granulocytic anaplasmosis (CGA). Peripheral venous blood samples were collected from 3 dog groups: (i) clinically healthy dogs (HD, n=400), (ii) clinically healthy hunting dogs (HHD, n=41), and (iii) dogs with a clinical suspicion of anaplasmosis (SD, n=29). Sampling was carried out in regions inhabited by I. ricinus (IR), I. persulcatus (IP), and in regions where both tick species were present (M). SNAP 4Dx test (IDEXX) was used to detect antibodies against A. phagocytophilum in the blood of all dogs; nested PCR was performed in selected dogs of the SD group. Seroprevalence for A. phagocytophilum was calculated and correlated with the prevalent tick species in the region. A. phagocytophilum seroprevalence was 11.0% in HD, 12% in HHD, and 17% in SD with no significant differences among groups. In the IR region, seroprevalence was 12.5% (34/272) while seroprevalence in the M region was 17% (13/76), and both were significantly higher than the seroprevalence of 2% in the IP region (2/93; p<0.0005). One CGA case was diagnosed. We conclude that A. phagocytophilum seroprevalence in Latvia is within the range reported from other European countries. CGA should be included in the differential list in Latvian dogs with appropriate clinical signs and laboratory abnormalities, especially in I. ricinus habitat areas.

Molecular evidence of vector-borne pathogens coinfecting dogs from Poland

Ticks of the genus Ixodes are vectors for many pathogens, including Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum and Rickettsia spp., and may also serve as vectors for Bartonella spp. However, the role of ticks in Bartonella transmission requires additional studies. The aim of this study was to investigate whether coinfection with two or more vector-borne pathogens can occur in the following three groups of dogs: I - dogs with suspected borreliosis (N = 92), II - dogs considered healthy (N = 100), and III - dogs with diagnosed babesiosis (N = 50). Polymerase chain reactions were performed to detect DNA of Anaplasma phagocytophilum, Rickettsia spp. and Bartonella spp. in the blood of dogs. In dogs of Group I, the DNA of both A. phagocytophilum and Bartonella sp. was detected (14% and 1%, respectively). In eight dogs, coinfection was indicated: A. phagocytophilum or Bartonella sp. with B. burgdorferi s.l. (the presence of antibodies against and/or DNA B. burgdorferi s.l.). In the case of five dogs positive for A. phagocytophilum DNA, no coinfection with B. burgdorferi s.l. was shown. In Group II, the DNA of A. phagocytophilum was detected in four dogs. In Group III, no pathogenic agents possibly transmitted by ticks were confirmed. No DNA of R. helvetica was detected in any of the groups studied.

Serological and molecular prevalence of Borrelia burgdorferi, Anaplasma phagocytophilum, and Ehrlichia species in dogs from Minnesota

A population of 731 naturally exposed pet dogs examined at a private practice in Baxter, Minnesota, an area endemic for Lyme disease and anaplasmosis, was tested by serological and molecular methods for evidence of exposure to or infection with selected vector-borne pathogens. Serum samples were tested by enzyme-linked immunosorbent assay (ELISA) for Anaplasma phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and for Dirofilaria immitis antigen. Blood samples from 273 dogs were also analyzed by polymerase chain reaction (PCR) for Anaplasma and Ehrlichia species DNA. Based on the owner history and the attending veterinarian's physical examination findings, dogs exhibiting illness compatible with anaplasmosis or borreliosis were considered clinical cases, and their results were compared to the healthy dog population. Antibodies to only A. phagocytophilum were detected in 217 (29%) dogs; to only B. burgdorferi, in 80 (11%) dogs; and seroreactivity to both organisms, in 188 (25%) dogs. Of 89 suspected cases of canine anaplasmosis or borreliosis, A. phagocytophilum or B. burgdorferi antibodies were detected in 22 dogs (25%) and 8 dogs (9%) respectively, whereas antibodies to both organisms were found in 38 dogs (43%). Ehrlichia canis antibodies and D. immitis antigen were each detected in 11 (1.5%) dogs. Anaplasma phagocytophilum DNA was amplified from 7 of 222 (3%) healthy dogs and 19 of 51 (37%) clinical cases. Seroreactivity to both A. phagocytophilum and B. burgdorferi was detected more frequently in suspected cases of anaplasmosis and/or borreliosis than seroreactivity to either organism alone. Based on PCR testing, A. phagocytophilum DNA was more prevalent in suspected cases of anaplasmosis or borreliosis than in healthy dogs from the same region.

Clinical features of canine granulocytic anaplasmosis in 18 naturally infected dogs

BACKGROUND

Anaplasma phagocytophilum, the causative agent of canine granulocytic anaplasmosis (CGA), is a Gram-negative intracellular organism transmitted by ixodid ticks. Thus far, only a few clinical studies evaluating dogs with CGA have been published.

OBJECTIVES

Evaluation of dogs naturally infected with A. phagocytophilum in which known co-infections were excluded.

ANIMALS

Eighteen dogs with CGA.

METHODS

Prospective study. The diagnosis of CGA was based on a positive PCR test result; dogs with co-infections were excluded. History, clinical findings, CBC, clinical biochemistry, infectious disease screening, diagnostic imaging, and the course of disease were evaluated.

RESULTS

CGA was diagnosed based on a positive PCR test for A. phagocytophilum; 10 dogs also had morulae in neutrophils. Six of 18 dogs were seronegative to A. phagocytophilum, the others were seropositive. All dogs were acutely ill. The most common clinical findings were lethargy, inappetence, fever, and splenomegaly. Abnormal laboratory results included thrombocytopenia, anemia, lymphopenia, hypoalbuminemia, and abnormally high plasma alkaline phosphatase activity. In 6 of 10 dogs tested, the platelet-bound antibody test was positive; Coombs' test was negative in 9 dogs. All dogs were treated with doxycycline and recovered. PCR testing as well as blood smear analysis for morulae were negative in 14 tested dogs 2-8 weeks after beginning treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinical findings in dogs with CGA were nonspecific. Positive platelet-bound antibody test results suggest immune-mediated platelet destruction as an important pathogenic mechanism. With correct diagnosis and treatment, prognosis is good.