Anaplasmosis in Cats. Control of Disease Consequences

Granulocytic anaplasmosis (GA) is an infectious multi-organ disease of humans and animals, characterized by pronounced anemia and thrombocytopenia. The etiological agents of the disease are microorganisms of the order Rickettsiales, family Anaplasmataceae.

Anaplasma spp., Ehrlichia spp., and Rickettsia spp. are pathogens that infect many mammal species, but the active disease phase occurs in only a small number of infected animals.

Anaplasma phagocytophilum is the most common pathogen causing clinical manifestations of the disease.

Anaplasma spp. are obligate intracellular Gram-negative coccoid microorganisms, members of the order Rickettsiales, infecting humans and a wide range of domestic and wild animals worldwide. They usually have low host specificity, and some animals may be only carriers of the infection.

The causative agents of anaplasmosis are transmitted through the bite of infected ixodid ticks and are intravacuolar organisms that reproduce in the hematopoietic cells of the body. They form cytoplasmic inclusion bodies: small elementary bodies (diameter 0.2–0.4 µm), larger reticular bodies and morulae (diameter up to 2–6 µm). Anaplasma phagocytophilum multiplies in myeloid cells (mainly neutrophils) and is the causative agent of granulocytotropic anaplasmosis. Natural reservoirs of infection are wild small mammals.

In Europe, two tick species transmit the infection: Rhipicephalus sanguineus sensu lato and Ixodes ricinus.

Pathogenesis

There is limited information about the pathogenesis of anaplasmosis in cats. A small number of studies have been conducted on experimental infection and the effects of infection on cats.

A study involving intraperitoneal experimental infection of cats with A. phagocytophilum resulted in a mild disease course accompanied by transient fever, not associated with changes in appetite or general condition. Hematological studies showed slight leukopenia, neutrophilia, lymphopenia, and pronounced anemia. Biochemical blood tests revealed notable elevation of liver enzymes, especially ALT and AST.

Clinical Signs

Cats naturally exposed to infected tick carriers typically develop clinical signs of granulocytic anaplasmosis shortly after infection. Symptoms are mostly nonspecific, including fever, anorexia, lethargy, conjunctivitis, and dehydration. Lymphadenopathy, lameness and joint swelling, nasal bleeding, and abdominal pain on palpation have also been reported.

Overall, the clinical course is usually short and mild, with rapid stabilization following antibiotic therapy.

Laboratory Changes

Hematological changes include mild to moderate thrombocytopenia, hemolytic anemia, lymphopenia, and eosinopenia; however, leukocytosis may occur if concurrent diseases are present.

Biochemical changes include increased serum protein levels, especially globulins; elevated liver enzymes: ALT, AST, GGT; and bilirubin.

Diagnosis

Clinical suspicion of anaplasmosis (rickettsiosis) usually arises in endemic areas with ectoparasites (fleas and ticks) in stray or domestic cats that are not regularly treated with antiparasitic agents. The first clinical symptom is fever.

Detection of the Infectious Agent

Cytological examination of blood smears may reveal Anaplasma phagocytophilum inclusion bodies (morulae) in 1–24% of circulating neutrophils in cats with natural granulocytotropic anaplasmosis.

In experimentally infected cats, morulae appear 7–9 days post-infection or within the first 10 weeks after a tick bite.

PCR blood testing is a sensitive and specific method for early confirmation of diagnosis during the acute clinical phase when antibody tests are often still negative.

Detection of Antibodies

Antibodies to rickettsial infections can be detected by immunofluorescence assay (IFA).

Antibodies to A. phagocytophilum were detected in experimental studies within 14 days post-infection. Seroconversion, i.e., the formation of specific antibodies, also occurs during natural infection, even in cats undergoing antibiotic therapy.

In cats exposed to infected ticks, antibodies against A. phagocytophilum appeared 2–6 weeks post-invasion.

Therapy

No controlled studies have evaluated the efficacy of drugs for treating rickettsioses in cats. However, doxycycline is considered the first-line antibiotic, prescribed at a dose of 5 mg/kg orally every 12 hours. The treatment course is 28 days.

When administering the drug, the risk of esophagitis after oral intake should be considered, so the animal must be given food and/or water to ensure the tablet passes into the stomach.

Prognosis

Clinical improvement is observed within 24–48 hours after starting antibiotic therapy. Cats usually respond well to treatment but may remain latent carriers of the infection.

Therefore, continuous periodic monitoring of clinical status and laboratory tests is recommended to prevent disease relapse.

Clinical Case

Cat Tsypa, a domestic short-haired cat weighing 6.3 kg, was imported from Cyprus 3 weeks ago. The history included intermittent fever, lethargy, and anorexia. A tick was removed from the cat’s body 4 weeks ago. Clinical symptoms were progressive, and the owners sought veterinary care. Blood analysis showed hemolytic anemia and thrombocytopenia (see below). Biochemical blood tests revealed significant elevation of liver transaminases.

Blood smears showed morulae in neutrophils identified as Anaplasma species.

IFA revealed antibodies to A. phagocytophilum, indicating a chronic infection (more than 14 days).

The cat was treated with doxycycline (5 mg/kg twice daily) for 21 days. The general condition began improving by day 7 of treatment.

Clinical Blood Analysis (cats)

Parameters, results by dates, and reference norms:

1. Red blood cells (RBC), x10⁹/L: 03.02.24 — 3,9;  20.02.24 — 5,93; 03.03.25 — 6,3

2. Hemoglobin (Hb), g/L: 03.02.24 — 89,0; 20.02.24 — 120,0; 03.03.25 — 128,0

Norm: 90–155

3. Hematocrit (Hct), %:  03.02.24 — 75,0; 20.02.24 — 35,0; 03.03.25 — 37,0

Norm: 26–48

4. Platelets (PLT), x10⁹/L: 03.02.24 — 6,4; 20.02.24 — 204; 03.03.25 — 198

Norm: 200–630

5. White blood cells (WBC), x10⁹/L: 03.02.24 — 7,0; 20.02.24 — 6,3 03.03.25 — 9,7

Norm: 5.5–19.0

6. Band neutrophils, %: 03.02.24 — 5; 20.02.24 — 4; 03.03.25 — 1

Norm: 0–5

7. Segmented neutrophils, %: 03.02.24 — 66; 20.02.24 — 62; 03.03.25 — 61

Norm: 35–75

8. Eosinophils, %:  03.02.24 — 0; 20.02.24 — 0; 03.03.25 — 0

Norm: 0–8

9. Basophils, %: 03.02.24 — 0; 20.02.24 — 0; 03.03.25 — 1

Norm: 0–1

10. Monocytes, %: 03.02.24 — 4; 20.02.24 — 4; 03.03.25 — 3

Norm: 1–4

11. Lymphocytes, %: 03.02.24 — 25; 20.02.24 — 3; 03.03.25 — 35

Norm: 28–60

20.02.2025

The owners came to the clinic for a follow-up examination. The general condition is satisfactory, appetite is reduced, slight dehydration is observed, no episodes of fever have been recorded. Weight – 6.3 kg. Complaints of occasional vomiting (1–2 times per week), mostly on an empty stomach. On physical examination:

- Mucous membranes are pale pink, capillary refill time up to 2 seconds;

- Body temperature – 38.8°C;

- Heart rate – 130 beats per minute;

- Respiratory rate – 27 breaths per minute.

The abdominal wall is not tense; auscultation reveals no cardiac rhythm disturbances. Regional lymph nodes are not enlarged.

Cypa has been receiving doxycycline therapy for 18 days.

According to laboratory tests: marked elevation of liver enzymes (see below); ELISA test – Anaplasma spp. antibodies not detected.

Biochemical blood analysis (cats)

Parameters, results by dates, and reference norms:

1. ALT (alanine aminotransferase), U/L: 20.02.24 — 67,4; 20.02.25 — 244,2

Norm:10–50

2. AST (aspartate aminotransferase), U/L: 20.02.24 — 57,3; 20.02.25 — 128,8

Norm: 10–40

3. Alkaline phosphatase, U/L: 20.02.24 — 73,4; 20.02.25 — 281,9

Norm: 10–65

4. GGT (gamma-glutamyl transferase), U/L: 20.02.24 — 3,6; 20.02.25 — 1,6

Norm: 0–10

5. Creatinine, µmol/L: 20.02.24 — 118,6; 20.02.25 — 117,1

Norm: 40–130

6. Urea, mmol/L: 20.02.24 — 6,05; 20.02.25 — 9,74

Norm: 5.0–11.0

7. Glucose, mmol/L: 20.02.24 — 6,8; 20.02.25 — 6,3

Norm: 3.2–6.9

8. Total protein, g/L;2 0.02.24 — 70,0; 20.02.25 — 79,5

Norm: 55–80

9. Albumin, g/L: 20.02.24 — 26,1; 20.02.25 — 25,6

Norm: 24–43

Ultrasound of the Biliary System

Liver: Echogenicity is moderately increased (lipidosis, chronic hepatopathy), echotexture is homogeneous, not enlarged, contours are smooth, borders are clear. The free edge is sharp, vascular pattern is moderately expressed. Intrahepatic bile ducts are not dilated. No space-occupying lesions detected.

Gallbladder: Typical shape, moderately filled (2.00 x 1.01 cm), wall thickness 0.13–0.14 cm, contents are heterogeneous (slight mural mobile sludge — chronic cholecystitis), gallbladder duct not dilated, common bile duct thickness 0.21 cm.

For stabilization of the cat’s general condition, infusion therapy with crystalloid solutions and additional symptomatic therapy are recommended:

1. Doxycycline – 5 mg/kg twice daily for 3 days.

2. Detoxol (solution) – 1 ml intravenously twice daily for 14 days.

3. Maropitant – 1 mg/kg intravenously once daily.

4. Famotidine ("Kvamatele") infusion solution – 1 mg/kg twice daily.

5. Ursodeoxycholic acid – 15 mg/kg orally once daily at night.

6. Cyanocobalamin – 500 mcg per cat intramuscularly once a week for 6 weeks.

7. Folic acid – 200 mcg per cat orally once daily for 4 weeks.

8. Dietary regimen to support liver function.

9. Ectoparasite treatments every 3 weeks.

In this case, the most challenging aspect was communication with the owners regarding the exact life history of the cat and the lack of diagnostic conclusions made in the region, which is endemic for rickettsioses.

There was concern about the condition of the biliary system. The cat had not undergone regular health monitoring every 6–12 months, so the duration of the disease process was unclear.

Symptomatic therapy was prescribed for the animal, with the key drug being "Detoxol" by “VETSINTEZ”.

The active ingredient in this drug is S-adenosylmethionine (SAMe), a natural molecule that is a key metabolite important for hepatocyte function. This molecule is produced by body cells from the amino acid methionine and adenosine triphosphate and plays an important role in immune regulation by restoring cellular membranes in many organs, primarily the liver.

SAMe crosses the blood-brain barrier, thus playing a role in the production and metabolism of neurotransmitters such as serotonin, melatonin, and dopamine in the brain.

Additionally, S-adenosylmethionine increases the levels of natural glutathione in the body. Glutathione is a powerful antioxidant that protects liver cells from the effects of toxic factors and apoptosis.

It has been proven that exogenous administration of SAMe improves hepatocellular function both in vitro and in vivo without causing cytotoxic effects.

It is also worth noting that folic acid and vitamin B12 are essential co-nutrients in the metabolism and accumulation of ademetionine.

"Detoxol" by “VETSINTEZ” comes in two forms: vials with powder containing 0.19 g (1.45 ml) and 0.38 g (2.85 ml) of active substance with solvent, which is convenient for use in small domestic animals.

03.03.2025

Two weeks later, a follow-up examination of the cat "Tsipa" was recommended. At the visit, the cat showed social behavior. According to the owners, during the 2 weeks, only 1 episode of vomiting undigested food with some hair was observed, after which the general condition and appetite remained stable. Owners also noted a decrease in stress episodes related to the cat’s recent relocation.

According to biochemical blood tests performed during the prescribed therapy, liver enzyme levels significantly decreased. The animal was advised to continue the dietary regimen and symptomatic oral therapy and to return for a control examination in 2 weeks. Overall, Tsipa’s condition was within physiological norms. The abdominal wall was not tense, and the cat showed no signs of stress during the visit and ate treats.

Based on this clinical case, the effectiveness of "Detoxol" by “VETSINTEZ” as adjunctive therapy for hepatopathies of various etiologies can be confidently confirmed, including those arising on the background of transmissible diseases.

Prevention of Granulocytic Anaplasmosis Caused by Anaplasma phagocytophilum

Since the main carriers of rickettsial infections are ticks, regular treatment of cats and dogs with ectoparasiticides, especially in endemic regions, is the only preventive method against rickettsioses.

Author: Lebedyk Khrystyna, Veterinarian, Specialist in Cat Diseases, Oncologist, Endocrinologist.