Association between Gallbladder Ultrasound Findings and Bacterial Culture of Bile in 70 Cats and 202 Dogs.

BACKGROUND: Bacterial cholecystitis often is diagnosed by combination of gallbladder ultrasound (US) findings and positive results of bile culture. The value of gallbladder US in determining the likelihood of bile bacterial infection in cats and dogs with suspected biliary disease is unknown. HYPOTHESIS/OBJECTIVES: To determine the value of gallbladder US in predicting bile bacterial culture results, identify most common bacterial isolates from bile, and describe complications after cholecystocentesis in cats and dogs with suspected hepatobiliary disease. ANIMALS: Cats (70) and dogs (202) that underwent an abdominal US and submission of bile for culture were included in the study. METHODS: A cross-sectional study design was used to determine the association of gallbladder US abnormalities and the results of bile cultures, and complications of cholecystocentesis. RESULTS: Abnormal gallbladder US had high sensitivity (96%) but low specificity (49%) in cats with positive and negative results of bile bacterial culture, respectively. Cats with normal gallbladder US findings were unlikely to have positive bile bacterial culture (negative predictive value of 96%). Gallbladder US had lower sensitivity (81%), specificity (31%), positive predictive value (20%), and negative predictive value (88%) in dogs. The most common bacterial isolates were of enteric origin, the prevalence being higher in cats. Incidence of complications after cholecystocentesis was 3.4%. CONCLUSIONS AND CLINICAL IMPORTANCE: Gallbladder US has a high negative predictive value for bile culture results in cats. This modality is less predictive of infection in dogs. Percutaneous US-guided cholecystocentesis has a low complication rate.

Intermittent At-Home Suctioning of Esophageal Content for Prevention of Recurrent Aspiration Pneumonia in 4 Dogs with Megaesophagus.

BACKGROUND: Megaesophagus carries a poor to guarded prognosis due to death from aspiration pneumonia. Options for medical management of regurgitation are limited to strategic oral or gastrostomy tube feeding. OBJECTIVES: To describe the use and efficacy of intermittent esophageal suctioning to prevent regurgitation and associated episodes of aspiration pneumonia in dogs with megaesophagus. ANIMALS: Four dogs with acquired idiopathic megaesophagus and recurrent aspiration pneumonia. METHODS: Retrospective review of medical records of dogs with megaesophagus in which intermittent suctioning of esophageal content was employed for management of recurrent aspiration pneumonia. RESULTS: Intermittent suctioning of the esophagus was initiated in 4 dogs after failure of strict gastrostomy tube feeding failed to prevent regurgitation and repeated episodes of aspiration pneumonia. Suctioning was accomplished by esophagostomy tube in 3 dogs and per os in 1 dog. After initiation of esophageal suctioning, dogs survived for a median of 13.5 additional months (range, 10-30 months) during which time 2 dogs had no additional episodes of aspiration pneumonia and 2 dogs had infrequent episodes of pneumonia, but aspiration was suspected to be a contributing factor in their death. Complications included clogging of the esophagostomy tube, esophagostomy site infections, and esophagitis. CONCLUSIONS AND CLINICAL IMPORTANCE: Use of intermittent esophageal suctioning in dogs with megaesophagus that continue to regurgitate despite gastrostomy tube feedings can reduce or abolish clinical episodes of aspiration pneumonia.

Mechanisms of Tritrichomonas foetus Pathogenicity in Cats with Insights from Venereal Trichomonosis.

Almost 20 years has passed since trichomonosis was first recognized as a potential cause of diarrhea in domestic cats. Despite progress in confirming disease causation, developing means for diagnosis, and identifying approaches to treatment of the infection, we still know very little about how this parasite causes diarrhea. With increasing recognition of resistance of trichomonosis to treatment with 5-nitroimidazole drugs, new treatment strategies based on an understanding of disease pathogenesis are needed. In this review, lessons learned from the pathogenesis of venereal trichomonosis in people and cattle are applied to clinical observations of trichomonosis in cats in effort to generate insight into areas where further research may be beneficial.

Association of Gallbladder Mucocele Histologic Diagnosis with Selected Drug Use in Dogs: A Matched Case-Control Study.

BACKGROUND: The cause of gallbladder mucocele (GBM) formation in dogs currently is unknown. Many available drugs represent a newer generation of xenobiotics that may predispose dogs to GBM formation. OBJECTIVE: To determine if there is an association between the histologic diagnosis of GBM in dogs and administration of selected drugs. ANIMALS: Eighty-one dogs with a histologic diagnosis of GBM and 162 breed, age, and admission date-matched control dogs from a single referral institution. METHODS: Medical records of dogs with GBM and control dogs from 2001 to 2011 were reviewed. Owner verification of drug history was sought by a standard questionnaire. Reported use of heartworm, flea, and tick preventatives as well as nonsteroidal anti-inflammatory drugs, analgesics, corticosteroids, or medications for treatment of osteoarthritis was recorded. RESULTS: Dogs with GBM were 2.2 times as likely to have had reported use of thyroxine (as a proxy for the diagnosis of hypothyroidism) as control dogs (95% confidence interval [CI], 0.949-5.051), 3.6 times as likely to have had reported treatment for Cushing's disease (95% CI, 1.228-10.612), and 2.3 times as likely to have had reported use of products containing imidacloprid (95% CI, 1.094-4.723). Analysis of a data subset containing only Shetland sheepdogs (23 GBM and 46 control) indicated that Shetland sheepdogs with GBM formation were 9.3 times as likely to have had reported use of imidacloprid as were control Shetland sheepdogs (95% CI, 1.103-78.239). CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides evidence for an association between selected drug use and GBM formation in dogs. A larger epidemiologic study of Shetland sheepdogs with GBM formation and exposure to imidacloprid is warranted.

Cysteine protease activity of feline Tritrichomonas foetus promotes adhesion-dependent cytotoxicity to intestinal epithelial cells.

Trichomonads are obligate protozoan parasites most renowned as venereal pathogens of the reproductive tract of humans and cattle. Recently, a trichomonad highly similar to bovine venereal Tritrichomonas foetus but having a unique tropism for the intestinal tract was recognized as a significant cause of colitis in domestic cats. Despite a high prevalence, worldwide distribution, and lack of consistently effective drugs for treatment of the infection, the cellular mechanisms of T. foetus pathogenicity in the intestinal tract have not been examined. The aims of this study were to determine the pathogenic effect of feline T. foetus on porcine intestinal epithelial cells, the dependence of T. foetus pathogenicity on adhesion of T. foetus to the intestinal epithelium, and the identity of mediators responsible for these effects. Using an in vitro coculture approach to model feline T. foetus infection of the intestinal epithelium, these studies demonstrate that T. foetus promotes a direct contact-dependent activation of intestinal epithelial cell apoptosis signaling and progressive monolayer destruction. Moreover, these pathological effects were demonstrated to be largely dependent on T. foetus cell-associated cysteine protease activity. Finally, T. foetus cysteine proteases were identified as enabling cytopathic effects by promoting adhesion of T. foetus to the intestinal epithelium. The present studies are the first to examine the cellular mechanisms of pathogenicity of T. foetus toward the intestinal epithelium and support further investigation of the cysteine proteases as virulence factors in vivo and as potential therapeutic targets for ameliorating the pathological effects of intestinal trichomonosis.

Ronidazole pharmacokinetics in cats following delivery of a delayed-release guar gum formulation.

Ronidazole (RDZ) is the only known effective treatment for feline diarrhea caused by Tritrichomonas foetus. This study aimed to develop guar gum-coated colon-targeted tablets of RDZ and to determine the pharmacokinetics of this delayed-release formulation in cats. Guar gum-coated tablets were administered orally once to five healthy cats (mean dose 32.3 mg/kg). The tablets were then administered once daily for 5 days to four cats (mean dose 34.5 mg/kg), and absorption studies repeated on day 5. Plasma was collected and analyzed for RDZ concentration, and pharmacokinetic noncompartmental and deconvolution analysis were performed on the data. There was negligible RDZ release until after 6 h, and a delayed peak plasma concentration (mean Cmax 28.9 µg/mL) at approximately 14.5 h, which coincides with colonic arrival in cats. Maximum input rate (mg/kg per hour) occurred between 6 and 16 h. This delayed release of ronidazole from guar gum-coated tablets indicates that release of RDZ may be delayed to deliver the medication to a targeted area of the intestine. Repeated dosing with guar gum tablets to steady-state did not inhibit drug bioavailability or alter the pharmacokinetics. Such targeted RDZ drug delivery may provide improved efficacy and reduce adverse effects in cats.

Feline Tritrichomonas foetus adhere to intestinal epithelium by receptor-ligand-dependent mechanisms.

Tritrichomonas foetus (TF) is a protozoan that infects the feline ileum and colon resulting in chronic diarrhea. Up to 30% of young purebred cats are infected with TF and the infection is recognized as pandemic. Only a single drug, characterized by a narrow margin of safety and emerging development of resistance, is effective for treatment. While the venereal pathogenicity of bovine TF is attributed to adherence to uterovaginal epithelium, the pathogenesis of diarrhea in feline TF infection is unknown. The aim of this study was to establish an in vitro model of feline TF adhesion to intestinal epithelium. Confluent monolayers of porcine intestinal epithelial cells (IPEC-J2) were infected with axenic cultures of feline TF that were labeled with [(3)H] thymidine or CFSE and harvested at log-phase. The effect of multiplicity and duration of infection, viability of TF, binding competition, formalin fixation and cytoskeletal inhibitors on adherence of feline TF to IPEC-J2 monolayers was quantified by liquid scintillation counting and immunofluorescence. [(3)H] thymidine and CFSE-labeled TF reproducibly adhered to IPEC-J2 monolayers. Clinical isolates of feline TF adhered to the intestinal epithelium in significantly greater numbers than Pentatrichomonas hominis, the latter of which is a presumably nonpathogenic trichomonad. Adhesion of TF required viable trophozoites but was independent of cytoskeletal activity. Based on saturation and competition binding experiments, adherence of feline TF to the epithelium occurred via specific receptor-ligand interactions. The developed model provides a valuable resource for assessing pathogenic mechanisms of feline TF and developing novel pharmacologic therapies for blocking the adhesion of feline TF to the intestinal epithelium.

Species identification of trichomonads and associated coinfections in dogs with diarrhea and suspected trichomonosis.

Trichomonads have been infrequently reported in the feces of dogs where their pathogenicity remains uncertain. It is currently unknown whether Tritrichomonas foetus or Pentatrichomonas hominis is identified more commonly in dogs with trichomonosis or how often these infections are accompanied by concurrent enteric infectious agents. The objective of this study was to determine the identity of trichomonads present in a series of 38 unsolicited canine diarrheic fecal samples submitted for T. foetus diagnostic polymerase chain reaction (PCR) testing between 2007 and 2010. We also examined each fecal sample for an association of trichomonosis with concurrent infection using a convenient real-time PCR panel for nine gastrointestinal pathogens. P. hominis, T. foetus, or both were identified by PCR in feces of 17, 1, and 1 dogs respectively. Feces from the remaining 19 dogs were PCR negative for T. foetus, P. hominis and using broader-spectrum Trichomonadida primers. The total number and specific identities of concurrent enteropathogens identified did not differ between fecal samples from dogs that were or were not identified by PCR as infected with trichomonads. These results suggest that P. hominis infection is more frequently identified than T. foetus infection in diarrheic dogs with trichomonosis and that concurrent enteropathogen infection is common in this population.

Uropathogenic E. coli promote a paracellular urothelial barrier defect characterized by altered tight junction integrity, epithelial cell sloughing and cytokine release.

The urinary bladder is a common site of bacterial infection with a majority of cases attributed to uropathogenic Escherichia coli. Sequelae of urinary tract infections (UTIs) include the loss of urothelial barrier function and subsequent clinical morbidity secondary to the permeation of urine potassium, urea and ammonia into the subepithelium. To date there has been limited research describing the mechanism by which this urothelial permeability defect develops. The present study models acute uropathogenic E. coli infection in vitro using intact canine bladder mucosa mounted in Ussing chambers to determine whether infection induces primarily a transcellular or paracellular permeability defect. The Ussing chamber sustains tissue viability while physically separating submucosal and lumen influences, so this model is ideal for quantitative measurement of transepithelial electrical resistance (TER) to assess alterations of urothelial barrier function. Using this model, changes in both tissue ultrastructure and TER indicated that uropathogenic E. coli infection promotes a paracellular permeability defect associated with the failure of umbrella cell tight junction formation and umbrella cell sloughing. In addition, bacterial interaction with the urothelium promoted secretion of cytokines from the urinary bladder with bioactivity capable of modulating epithelial barrier function including tumour necrosis factor-α, interleukin (IL)-6 and IL-15. IL-15 secretion by the infected bladder mucosa is a novel finding and, because IL-15 plays key roles in reconstitution of tight junction function in damaged intestine, this study points to a potential role for IL-15 in UTI-induced urothelial injury.

Documentation of in vivo and in vitro aerobic resistance of feline Tritrichomonas foetus isolates to ronidazole.

BACKGROUND: The mainstays of treatment for clinically important trichomonad infections are the 5-nitroimidazoles. Metronidazole resistance of feline Tritrichomonas foetus is presumed because of common treatment failure, and tinidazole does not consistently eradicate infection. To date, ronidazole is the only drug demonstrated as effective for treatment of cats infected with T. foetus. OBJECTIVE: To document in vivo treatment failure and identify underlying causes and in vitro conditions of resistance of feline T. foetus to ronidazole. ANIMALS: Two intact male Abyssinians failing>or=5 courses of treatment with increasing doses of 5-nitroimidazole drugs. An intact male Abyssinian documented to clear infection after treatment with a single course of ronidazole. METHODS: T. foetus isolates were cultured from feces and tested in vitro for susceptibility to ronidazole under aerobic and anaerobic culture conditions. A urogenital nidus of T. foetus infection was investigated by culture, polymerase chain reaction, or immunohistochemical testing of urogenital specimens. RESULTS: Resistance to ronidazole under aerobic conditions was uniquely identified in T. foetus isolated from cats with well-documented treatment failure. Treatment failure could not be attributed to reinfection, inappropriate treatment protocol, or presence of a urogenital nidus of infection. CONCLUSIONS AND CLINICAL IMPORTANCE: Clinical resistance to metronidazole, low efficacy of tinidazole, and present documentation of in vivo and in vitro resistance to ronidazole in some cats are consistent with a high level of cross resistance of feline T. foetus to 5-nitroimidazole drugs. Current lack of alternative drugs with clinical efficacy against feline T. foetus suggests that active investigation of other treatment approaches is warranted.

Fluorescence in situ hybridization for identification of Tritrichomonas foetus in formalin-fixed and paraffin-embedded histological specimens of intestinal trichomoniasis.

In the present study a highly species-specific oligonucleotide sequence of Tritrichomonas foetus 18S rRNA was used to design an antisense probe for identification of T. foetus in formalin-fixed and paraffin-embedded histological specimens by means of fluorescence in situ hybridization (FISH). Using archival histological specimens from several species with light microscopic evidence of intestinal trichomoniasis, and under optimized hybridization conditions, the probe positively identified trichomonads in colonic specimens from piglets and a kitten with PCR-confirmed T. foetus infection. Neither positive hybridization of the probe or PCR amplification of T. foetus DNA was observed in histological specimens from hamster (Tritrichomonas muris), turkey, nor mouse (Entamoeba muris) intestinal protozoal infections. Sequence-specific binding of the probe was further verified by successfully out-competing the hybridization with 10 x molar excess unlabeled probe and failure of a labeled sense probe to hybridize. The FISH assay described here enables simultaneous location and molecular identification of T. foetus in formalin-fixed and paraffin-embedded histological specimens of intestinal trichomoniasis. The methods employed are likely to also be applicable to probes designed for specific recognition of other trichomonad species, especially in mammalian tissue where red blood cell auto-fluorescence can be easily differentiated from the hybridization signal of trichomonads.

Feline diarrhoea associated with Tritrichomonas cf. foetus and Giardia co-infection in an Australian cattery.

A 10-week-old female Ocicat was presented at a primary care feline veterinary practice for failure to thrive and diarrhoea. Numerous trophozoites, atypical for Giardia sp., were detected on a direct faecal examination, in addition to Giardia cysts. Although the failure to thrive and diarrhoea resolved following treatment for giardiasis, further diagnostic tests performed on faecal specimens from the kitten and 15 other Ocicats from the same cattery, including culture of trophozoites in In Pouch medium, PCR testing and molecular sequencing of PCR amplicons, confirmed infection with Tritrichomonas cf. foetus. This is the first report in Australia of feline trichomoniasis, which appears to be an emerging infectious disease of cats. Pertinent information regarding the clinical features, diagnosis, therapy, and potential source of feline trichomoniasis within Australia are discussed.

Histologic features associated with tritrichomonas foetus-induced colitis in domestic cats.

Tritrichomonas foetus is a venereal pathogen of naturally bred cattle. In domestic cats, T. foetus colonizes the colon, resulting in chronic, large-bowel diarrhea. The infection is prevalent among young, densely housed cats, and there is no effective treatment. To the authors' knowledge, the characteristic microscopic lesions of T. foetus infection in naturally infected cats have not been described. The aim of the study reported here was to characterize the histologic changes in the colon of seven cats with T. foetus infection and chronic diarrhea. All cats were 1 year old or younger (mean, 6.7 +/- 1.7 months), and a diagnosis of T. foetus infection was made on the basis of direct fecal smear examination (five cats), fecal culture in InPouch TF medium (four cats), single-tube nested polymerase chain reaction (PCR) analysis of DNA extracted from feces (two cats), or observation of trichomonads in sections of colon followed by PCR confirmation on DNA extracted from paraffin-embedded tissue (two cats). The presence of colonic trichomonads was the most diagnostic histologic feature. Organisms were identified in all cats, but in only 24 of 43 (56%) sections of colon. Trichomonads were generally present in close proximity to the mucosal surface and less frequently in the lumen of colonic crypts. The presence of colonic trichomonads was consistently associated with mild-to-moderate lymphoplasmacytic and neutrophilic colitis, crypt epithelial cell hypertrophy, hyperplasia and increased mitotic activity, loss of goblet cells, crypt microabscesses, and attenuation of the superficial colonic mucosa. In two of the cats, histologic lesions were more severe and were associated with invasion of trichomonads into the lamina propria and/or deeper layers of the colon.

Experimental infection of cats with Tritrichomonas foetus.

OBJECTIVE: To determine whether infection with Tritrichomonas foetus causes diarrhea in specific-pathogen-free or Cryptosporidium coinfected cats. ANIMALS: 4 cats with subclinical cryptosporidiosis (group 1) and 4 specific-pathogen-free cats (group 2). PROCEDURE: Cats were infected orogastrically with an axenic culture of T. foetus isolated from a kitten with diarrhea. Direct microscopy and protozoal culture of feces, fecal character, serial colonic mucosal biopsy specimens, and response to treatment with nitazoxanide (NTZ; group 1) or prednisolone (groups 1 and 2) were assessed. RESULTS: Infection with T. foetus persisted in all cats for the entire 203-day study and resulted in diarrhea that resolved after 7 weeks. Group-1 cats had an earlier onset, more severe diarrhea, and increased number of trichomonads on direct fecal examination, compared with group-2 cats. Use of NTZ eliminated shedding of T. foetus and Cryptosporidium oocysts, but diarrhea consisting of trichomonad-containing feces recurred when treatment was discontinued. Prednisolone did not have an effect on infection with T. foetus but resulted in reappearance of Cryptosporidium oocysts in the feces of 2 of 4 cats. During necropsy, T. foetus was isolated from contents of the ileum, cecum, and colon. Tritrichomonas foetus organisms and antigen were detected on surface epithelia and within superficial detritus of the cecal and colonic mucosa. CONCLUSIONS AND CLINICAL RELEVANCE: After experimental inoculation in cats, T. foetus organisms colonize the ileum, cecum, and colon, reside in close contact with the epithelium, and are associated with transient diarrhea that is exacerbated by coexisting cryptosporidiosis but not treatment with prednisolone.

Granulomatous disease associated with Bartonella infection in 2 dogs.

Shortly after removal of an engorged tick from the left ear, a 4-year-old Greyhound was referred for evaluation of fever and a rapidly enlarging mass in the region of the left submandibular lymph node. Histopathologic evaluation of the lymph node resulted in a diagnosis of severe granulomatous lymphadenitis. An 11-year-old mixed-breed dog was referred for evaluation of a 6-week history of serous nasal discharge. Histologic examination of a surgical biopsy from a nasal mass indicated multifocal granulomatous inflammation with fibrosis. Serum samples obtained from both dogs were reactive by immunofluorescent assay to Bartonella vinsonii subsp. berkhoffii antigens (reciprocal titers of 128). Although Bartonella organisms were not isolated by lysis centrifugation blood culture, Bartonella DNA was amplified from tissue samples obtained from each dog (lymph node biopsy from dog 1 and nasal biopsy from dog 2) using primers that amplify a portion of the 16S rRNA gene followed by Southern blot hybridization using a genus-specific probe. Additionally, restriction fragment length polymorphism (RFLP) analysis of a Bartonella-specific citrate synthase gene product obtained from dog 2 resulted in a restriction pattern identical to B. vinsonii subsp. berkhoffii. This is the 1st report of granulomatous disease in dogs associated with Bartonella infection.

Evaluation of the effect of pleural effusion on central venous pressure in cats.

This study was undertaken to determine if pleural effusion (PEF) increases central venous pressure (CVP) in cats, to define any relationship between volume of PEF and CVP and to ascertain the significance of CVP alterations in cats having PEF and suspected right heart failure (RHF). CVP was measured from a jugular vein before (CVPpre) and after (CVPpost) bilateral thoracentesis in 9 cats with naturally occurring PEF and under experimental conditions in 3 spontaneously breathing anesthetized cats receiving graded intrathoracic infusion of saline. Volumes of introduced and recovered fluid were recorded. A significant decrease occurred in CVP after thoracentesis in cats with naturally occurring PEF (mean difference, 4.5 cm H2O; range, 0-7.0 cm H2O, P < .005). The magnitude of change in CVP was constant (r = 0.36, P > .05) over the range of volumes recovered (range, 95-450 mL or 16.4-90 mL/kg). Five cats had CVPpre suggestive of RHF (range, 8.16-20.4 cm H2O). After thoracentesis, RHF was ruled out in 1 cat (CVPpost, 4.08 cm H2O) and the CVP declined but remained abnormally high (9.52 cm H2O) in 1 cat with a mediastinal mass. In 2 cats with confirmed RHF (CVPpre, 20.4 and 16.3 cm H2O), CVP decreased after thoracentesis but remained abnormally high (CVPpost, 14.96 and 10.88 cm H2O). In 1 cat with noncardiogenic PEF and inadequate removal of fluid, CVPpost (8.16 cm H2O) did not decrease. Experimentally, a positive linear relationship was observed between CVP and volume of PEF. The threshold volume required to increase CVP (17 mL/kg) approximated that suggested by clinical observation (22 mL/kg). PEF increases CVP and can cause abnormally high CVP in the absence of RHF.

Diarrhea associated with trichomonosis in cats.

OBJECTIVE: To establish clinical features, course of illness, and treatment outcome of cats with diarrhea and concurrent infection with Trichomonas organisms. Prevalence of fecal trichomonads in a geographically comparable population of healthy indoor and feral cats also was assessed. DESIGN: Longitudinal study and a cohort study. ANIMALS: 32 cats with diarrhea and naturally acquired trichomonosis that were native to North Carolina, Virginia, Connecticut, and Tennessee; 20 healthy indoor cats; and 100 feral cats. PROCEDURE: Trichomonosis was diagnosed in 32 cats by identification of organisms in fresh feces or by protozoal culture of feces. RESULTS: Diarrhea associated with the large intestine and trichomonosis were diagnosed in 32 cats. Median age of the cats was 9 months; 23 cats were < or = 1 year old at the time of diagnosis. Two cats developed diarrhea accompanied by infection with Trichomonas organisms after the addition of an infected kitten into the home. Duration of diarrhea ranged from 2 days to 3 years. Six cats had a coexisting enteric infection. Treatment with antimicrobials improved fecal consistency and reduced the number of flagellates in the feces, but did not eliminate infection. Diarrhea (with microscopically detectable flagellates) was observed shortly after antibiotics were discontinued. Trichomonads were not recovered from feces of any healthy indoor or feral cats. CONCLUSIONS AND CLINICAL RELEVANCE: Our findings suggest that trichomonosis may be a cofactor in development of diarrhea in young cats. Trichomonas organisms were not identified as part of the indiginous fauna of healthy indoor or feral cats.

Acute renal failure in four cats treated with paromomycin.

Acute renal failure was diagnosed in 4 cats receiving paromomycin orally for treatment of infectious enteritis. All 4 cats responded to fluid therapy and recovered normal or near-normal renal function; however, 3 of the cats subsequently became deaf and developed cataracts. Toxicoses were attributed to a combination of an excessive dosage of paromomycin and absorption of the drug across injured intestinal mucosal epithelium. Pharmacokinetic studies are needed to further define the disposition of paromomycin after oral administration to cats.