Discover which kind of disease this Labrador Retriever has, plus what causes the disease and how it is transmitted and treated.
A 5-year-old Labrador Retriever was presented for a decreased appetite, low-grade fever, and moderately elevated liver enzymes. The physical exam showed mild icterus, a temperature of 103.5 °F, and was otherwise unremarkable. An ultrasound of the liver was performed and the changes were identified in Figure 1. Based on these images and clinical signs, which of the following is most likely?
a. Chronic active lymphoplasmacytic hepatitis
c. Histiocytic sarcoma
d. Copper-associated hepatopathy
Answer: b. Bartonellosis
The images of the liver show multiple coalescing heterogeneous masses, the largest up to 9.2 cm x 4.8 cm x 7.0 cm, without evidence of cavitation. Very few liver pathologies can be diagnosed on ultrasonographic appearance alone, including hepatic Bartonella infection. Given the ultrasonographic appearance and clinical signs however, bartonellosis was high on this dog’s differential list. Further diagnostics included enriched polymerase chain reaction (ePCR) testing for Bartonella organisms and indirect immunofluorescence assay (IFA) serology, as well as ultrasound-guided liver aspirates which confirmed pyogranulomatous inflammation. Aerobic and anaerobic cultures and toxoplasma enzyme-linked immunosorbent assay immunoglobulin M (IgM) and IgG testing were negative. The ePCR (both whole blood and liver aspirates) was negative; however, IFA serology was positive at 1:128 for B henselae and 1:64 for B koehlerae (there is suspicion that the positive B henselae may have been due to cross-reactivity to B koehlerae). The dog was treated with doxycycline at 5 mg/kg by mouth twice daily and enrofloxacin at 10 mg/kg by mouth once daily for 6 weeks with resolution of fever and inappetence and normalization of liver enzymes.
Chronic autoimmune hepatitis and copper-associated hepatopathy are relatively common causes of liver disease, particularly in middle-aged Labrador Retrievers. They should always be considered in cases of elevated liver enzymes without obvious neoplastic changes. Because of the heterogenous presentation and overlap between these diseases, as well as infectious and neoplastic causes, multiple diagnostics are often needed to make a diagnosis. Ultrasound is usually nonspecific, and there are no pathognomonic findings for bartonellosis; however, the solid, hypoechoic nodules deforming the hepatic margin raised the suspicion for a proliferative process (ie, neoplastic or granulomatous lesions) rather than a chronic inflammatory condition, which usually results in less demarcated lesions.
Bartonella is transmitted through bites from ticks, fleas, lice, and other vectors and can be associated with a panoply of clinical signs. These include endocarditis, polyarthritis, granulomatous rhinitis, anterior uveitis, idiopathic effusions, and lymphadenitis, as well as pyogranulomatous hepatitis.1 Seropositivity ranges depending on geographic region and exposure to vectors, with an overall US prevalence of about 3%.2 One study demonstrated that approximately 10% of healthy dogs and 26% of sick dogs were seropositive for Bartonella in the Southeast US3; the dog in this case had no history of travel outside of the Midwest.
Ideal treatment regimens for bartonellosis are not established, and rapid development of resistance is well recognized in Bartonella species.1, 4 For this reason, combination therapy such as doxycycline and enrofloxacin is often recommended, typically for at least 4 to 6 weeks.1, 4
Jessica Romine, DVM, DACVIM, is currently a small animal internal medicine specialist at Animal Referral Centre in Auckland, New Zealand. She has a special interest in interventional radiology and advanced imaging procedures.
Editors note: All veterinary technician content for this month is supported by Banfield Pet Hospital.