Common Canine Rickettsial Diseases: Overview & Preventi

Key Features of the Disease

This disease is prevalent in tropical and subtropical regions. The Haemaphysalis canis tick serves as a host for both Rickettsia canis and the canine Ehrlichia, making it a vector for both pathogens, often leading to mixed infections. It can also infect wild animals such as wolves, jackals, wild dogs, and foxes.

Clinical Symptoms

The incubation period for this disease ranges from 8 to 20 days. Symptoms include a sudden rise in body temperature, depression, drowsiness, mucous or purulent discharge from the mouth and nose, stiffness, edema in the limbs or lower abdomen, coughing, or difficulty breathing, decreased appetite, jaundice, vomiting, progressive weight loss, photophobia, and discharge of mucopurulent material from the eyes. In severe cases, anemia and hypotensive shock may occur, with some animals showing pale and bleeding mucous membranes in the mouth, nose, and reproductive tract, as well as hyphema and hematuria, and black stools. Mixed infections with Ehrlichia can lead to more severe symptoms. After 1 to 2 weeks, symptoms may subside and transition into a chronic phase, which can last up to 4 months. Reinfection can still present with acute symptoms.

Pathological Changes

The body becomes emaciated, anemic, with enlarged liver and spleen, scattered petechiae in the lungs, enlarged lymph nodes, severe jaundice (more pronounced when Ehrlichia is involved), ulceration and hemorrhage of the intestinal mucosa, and less common conditions such as pulmonary edema and pleural effusion.

Differential Diagnosis

(1) Rickettsial Disease in Dogs vs. Leptospirosis

Both diseases present with symptoms like fever, depression, jaundice, vomiting, and enlarged superficial lymph nodes. The distinction lies in the symptoms of leptospirosis, which include muscle pain, hematuria, oliguria, or urine that appears like soy sauce (dark teacolored), acute lymphadenopathy, and jaundiced mucous membranes. Postmortem examination reveals mucous membranes that are reddened and hemorrhagic, appearing dark red, with enlarged liver and brownish spots and hemorrhagic points. Darkfield microscopy of samples collected during the fever phase shows the characteristic "O," "S," and "C" shape of the pathogen.

(2) Rickettsial Disease in Dogs vs. Babesiosis

Both diseases exhibit symptoms like fever, depression, vomiting, and jaundiced mucous membranes. The difference is that dogs with babesiosis may have urine that is yellowishbrown or hematuric, and blood tests will reveal Babesia within the blood cells.

(3) Rickettsial Disease in Dogs vs. Clonorchiasis

Both diseases present with symptoms like progressive weight loss and jaundiced mucous membranes. The distinction is that dogs with clonorchiasis may have diarrhea, and postmortem examination may reveal ascites, worms in the bile ducts and gallbladder, and round, light bulblike eggs in feces.

Advice

Based on the analysis of the epidemiological characteristics and clinical symptoms, combined with hematology tests, biochemical tests, pathogen isolation and identification, and serological tests, a diagnosis can be made. During the acute phase of clinical symptoms, Rickettsia can often be found in the blood, lungs, liver, and spleen. Fresh disease material can successfully replicate the disease when inoculated into susceptible animals.

Preventive Measures

(1) Prevention

Pay attention to tick control on the premises. Dogs returning from tickinfested areas should be checked for ticks on their bodies. In highrisk areas, use DDT for spraying or 1% dipterex solution for dipping.

Treatment

The treatment principle is antibacterial and supportive therapy.

① Trimethoprimsulfamethoxazole (TMPSMX), 30 mg/kg body weight for dogs, taken orally twice daily for 3 to 4 days.

② Tetracycline, 1522 mg/kg body weight for dogs, taken orally three times daily for 3 to 4 days.

③ Chlortetracycline, 20 mg/kg body weight for dogs, taken orally three times daily.

④ Doxycycline, 510 mg/kg body weight for dogs, administered intravenously or intramuscularly twice daily for 10 to 11 days.

⑤ Imidocarb, 57 mg/kg body weight for dogs, administered subcutaneously or intramuscularly, repeated after 14 days; 25 mg/kg body weight for cats, administered intramuscularly, repeated after 14 days.