Management of bilateral uveitis in a Toxoplasma gondii-seropositive cat with histopathologic evidence of fungal panuveitis

A 5‐year‐old, neutered male Domestic Short‐haired cat was referred with a 5‐month history of anterior uveitis and cataract in the right eye. Clinical examination confirmed anterior uveitis and immature cataract in the right eye and chorioretinitis in the left eye. Ocular ultrasound showed a retinal detachment in the right eye. Diagnostic testing revealed elevated serum titers for Toxoplasma gondii. Anterior uveitis in the right eye and chorioretinitis in the left eye progressed, resulting in blindness despite a 21‐day course of clindamycin and aggressive topical medical management of uveitis. The right eye was enucleated and histopathologic evaluation of the globe revealed panuveitis and multiple organisms morphologically consistent with Histoplasma capsulatum. Systemic treatment with itraconazole was initiated. Vision returned after 3 months of treatment and complete resolution of the retinal hemorrhages with formation of a flat chorioretinal scar was noted after 6 months of therapy. Itraconazole was discontinued 7 months after starting therapy, at which time the funduscopic appearance of the chorioretinal scar had remained static for 1 month. The cat has remained visual without evidence of disease progression for 6 months following discontinuation of itraconazole.

Toxoplasma gondii infection in horses. A review

This review updates those written by Dubey and Beattie in 1988 (1988a) and by Tenter et al in 2000, on pathological and epidemiological aspects of Toxoplasma infection in horses. Under natural conditions, seroprevalence may variate from 0% up to 90%. This wide variation may be due to the sensitivity of the serological methods, to the age of animals, to the geographical area, and even to the hygienic condition of the farms and farm management. With few exceptions, horses are considered one of the less sensitive specie to the pathogenic effect of Toxoplasma gondii. In fact, neither under experimental nor under natural condition a genuine pathologic picture related to the toxoplasmic infection has been described. In one occasion the organism has been isolated from an eye condition and in others a connection between a higher frequency of unspecified pathological conditions and a positive response to serological test for Toxoplasma has been speculated. Diaplacental transmission and the following abortion have been only occasionally reported, and at least in one case in a quite trustworthy way, therefore it must be considered possible, though rare. Although infection of humans due to the consumption of horse meat has never been reported, the existence of a possible risk arouses by the demonstration of the presence of parasite stages in either naturally or experimentally infected horses, which resulted to be infective for mice and/or cats.

Chronic ocular lesions in tawny owls (Strix aluco ) injured by road traffic

The chronic ocular lesions suffered by 50 tawny owls (Strix aluco) injured by road traffic were investigated. They included non-healing corneal erosions, cataracts and retinal scarring, and periretinal membrane formation. The intraocular pressure was significantly lower in the eyes with intraocular inflammatory pathology and higher in the eyes with irido- or cyclodialysis than in ophthalmically normal eyes. Cicatritial retinal lesions were not associated with high titres of antibodies to Toxoplasma species. The findings correlate with those observed in human beings with eye injuries due to high-speed blunt trauma.

Prevalence of anti-Toxoplasma gondii antibodies in serum and aqueous humor samples from cats with uveitis or systemic diseases in France

Anti-Toxoplasma gondii antibodies were determined in serum and aqueous humor of two groups of cats in France: cats with uveitis (group 1, n=26) and cats with systemic disease (group 2, n=24) using an agglutination test. Titres above 1:64 were considered positive. IgG antibodies to T. gondii were detected in 10 serum samples from group 1 and in 10 serum samples from group 2, and in 2 aqueous humor samples from group 1 and in 1 aqueous humor samples from group 2. The distribution of ocular lesions according to the serological status of the animals indicated that lens luxation and buphthalmia were more frequent in T. gondii seropositive cats than in seronegative ones. The study reports a similar prevalence of anti-T. gondii antibodies in cats with uveitis and in cats without uveitis in France. Serological results must be analysed carefully and additional diagnostic tools is required.

Ultrastructural findings in feline corneal sequestra

OBJECTIVES

(1) To describe the ultrastructural features of corneal sequestra in cats; and (2) to enhance our understanding regarding the pathogenesis of feline corneal sequestration.

METHODS

Nine corneal sequestra were harvested via keratectomy from globes of nine cats. The sequestra were routinely fixed then postfixed for high resolution light and transmission electron microscopy (HR-LM and TEM, respectively). The tissues were embedded in Epon/Araldite. Sections of 0.5-microm thickness were cut and stained with 1% toluidine blue in 1% sodium tetraborate solution for HR-LM. Ultrathin sections were collected on copper grids and stained with uranyl acetate and Sato's lead stain for TEM. Ultrathin sections were examined and the images were captured on an Advantage HR CCD camera using a Hitachi 7500 electron microscope operated at 80 kV. Two healthy corneas from two cats were harvested immediately following euthanasia. These corneal tissues (control samples) were processed in the same manner as the corneal sequestra for HR-LM and TEM. A portion of each sequestrum was also submitted for polymerase chain reaction (PCR) testing for infectious agents including feline herpesvirus-1 (FHV-1), Toxoplasma gondii, Chlamydophila felis and Mycoplasma spp.

RESULTS

Ultrastructure of healthy corneal tissues revealed basal corneal epithelial cells aligned adjacent to a thin acellular layer similar to Bowman's layer with underlying tightly packed, regularly arranged, collagen fibrils oriented in different planes. Keratocytes were elongated and had long and irregularly shaped nuclei, and cytoplasm contained rough endoplasmic reticulum and abundant membrane-bound vesicles. In contrast, corneal sequestra contained varying amounts of an amorphous, electron-dense substance, continuous with intact basal epithelial basement membranes peripherally, and overlying corneal ulceration and loosely packed collagen fibrils. Remnants of necrotic keratocytes were seen in spaces between disarranged collagen layers. In all samples, occasional keratocytes exhibited morphology indicative of apoptosis including clumping and margination of chromatin, and shrunken cytoplasm. Varying degrees of inflammation were noted on HR-LM and TEM of affected corneas including peri- and intralesional neutrophils, lymphocytes, plasma cells, and macrophages. Corneal sequestra were FHV-1-positive (n = 3), FHV-1- and T. gondii-positive (n = 1), T. gondii-positive (n = 3), or negative for DNA of these infectious agents (n = 2) using PCR. All corneal sequestra were negative for DNA of Chlamydophila felis and Mycoplasma spp. using PCR.

CONCLUSIONS

Apoptosis may play a role in the pathogenesis of feline corneal sequestration independent of the presence of DNA of these infectious organisms. Prospective clinical studies are warranted to further understand the significance of T. gondii in relation to feline corneal sequestration.

Inoculation with Bartonella henselae followed by feline herpesvirus 1 fails to activate ocular toxoplasmosis in chronically infected cats

Infection by Toxoplasma gondii is very common in cats although most remain disease free. The factors that trigger development of uveitis in some cats infected with T gondii have not been elucidated, but infection by more than one organism may be contributory. In this study, cats chronically infected with T gondii were inoculated with Bartonella henselae followed by FHV-1 to test the hypothesis that immune stimulation by multiple infections will reactivate ocular toxoplasmosis. Anterior uveitis and chorioretinitis were not detected in the cats with chronic T gondii infection thus allowing rejection of the hypothesis using this experimental design.

Ocular and encephalic toxoplasmosis in canaries

In this report we describe the lesions produced by the protozoal organism, Toxoplasma gondii, in the eyes and brain of the common yellow canary (Serinus canaria). Nine of 15 birds in a flock were affected with blindness, which developed over a 3-mo span, and two birds developed torticollis. Microscopic alterations within the eye consisted of a nonsuppurative chorioretinitis with large numbers of macrophages that contained the tachyzoite form of T. gondii in the subretinal space, and aggregates of tachyzoites were found in the nerve fiber layer of the retina with and without necrosis. Tissue cysts with bradyzoites were scattered throughout the meninges and neuropil of the cerebrum and cerebellum. Both forms were confirmed by transmission electron microscopy in the eye and brain. Frozen brain samples reacted with T. gondii-specific cat sera in indirect fluorescent antibody tests. The source of infection was hypothesized to be from a stray cat the owner kept that had access to some of the bird feed. Treatment (trimethoprim 0.08 g/ml H2O and sulfadiazine 0.04 g/ml in water for 2 wk) was instituted by the referring veterinarian on the remaining birds. A second treatment regime was given for 3 wk. The owner of the canaries did not return for further treatment.

Toxoplasmosis

Toxoplasmosis in dogs and cats can cause chorioretinitis, anterior uveitis, or both. Ocular lesions are a common manifestation of generalized toxoplasmosis. The prevalence of toxoplasmosis as a cause of idiopathic anterior uveitis in cats is not clear, although there is a significant association between exposure to T. gondii and feline anterior uveitis. The pathogenesis of ocular toxoplasmosis may be different in humans and cats, and the anterior uveitis may represent a type of immune-mediated inflammation. A diagnosis is made by observing compatible clinical findings and obtaining supportive findings on serologic tests. Despite improved diagnostic techniques, including determination of IgM class antibodies and PCR testing, definitive diagnosis of ocular toxoplasmosis remains a challenge. Topical anti-inflammatory therapy should be used in cats with anterior uveitis, a positive serum titer, and no concurrent systemic signs. Systemic clindamycin should be given to cats with ocular and systemic signs and to cats with suggestive serology and idiopathic anterior uveitis that fails to respond to topical therapy alone.

Polymerase chain reaction for the detection of Toxoplasma gondii within aqueous humor of experimentally-inoculated cats

The purpose of this study was to determine the temporal appearance of T. gondii in aqueous humor of cats orally inoculated with T. gondii using polymerase chain reaction (PCR) for the detection of the B1 gene. Serum and aqueous humor were collected from five SPF cats prior to oral inoculation with T. gondii and days 7, 14, 21, 28, 42, 84, 140, 147, 154, 161, 168, and 182 after inoculation. Cats were inoculated orally with T. gondii tissue cysts on day 0 and day 140. T. gondii-specific IgM and IgG were measured in serum and aqueous humor from the cats at each sample data. T. gondii B1 gene PCR was performed on all the aqueous humor samples and the amplified DNA was detected by Southern blotting. Chorioretinitis developed in three out of the five cats, but anterior uveitis was not detected. All cats developed T. gondii-specific IgG titers in serum, and had T. gondii-specific IgG C-values > 1 in both eyes at varying times during the study. T. gondii was detected by PCR and Southern blotting in aqueous humor in both eyes of all cats at times varying from days 14-84 after primary inoculation and days 14-42 after challenge inoculation.

Elevated interleukin 6 activity in aqueous humor of cats with uveitis

The purpose of this study was to assess the role of interleukin 6 (IL-6) in feline uveitis by measuring IL-6 activity in the serum and aqueous humor of cats. Serum and aqueous humor was collected from clinically normal, random source cats (n = 10); clinically normal, specific-pathogen free cats experimentally inoculated with Toxoplasma gondii strain ME49 and sampled sequentially for 20 months (n = 4); and client-owned cats with uveitis (n = 27). Interleukin 6 activity was measured in each sample. Client-owned cats with uveitis were also evaluated for evidence of present or prior exposure to T. gondii, feline leukemia virus, feline immunodeficiency virus, and feline coronaviruses. Interleukin 6 activity was non-detectable or low in serum from cats of each group. Interleukin 6 activity was not detected in aqueous humor of clinically normal cats. Interleukin 6 activity was detected in 22/27 (81.5%) aqueous humor samples from cats with uveitis, with a range of 28.9 U ml(-1)-15702.9 U ml(-1) (mean = 1911.9 U ml[-1], SD = 3946.7 U ml[-1]). Serologic evidence of exposure to T gondii, feline immunodeficiency virus, feline leukemia virus, or a coronavirus was present in 21/27 (77.8%) cats with uveitis. Interleukin 6 was detected in the aqueous humor of 18/21 (85.7%) and 3/6 (50%) of the cats with and without serologic evidence of exposure to one to the infectious diseases, respectively. Statistically significant increases in mean IL-6 activity in aqueous humor were found for cats with any evidence of infection with T. gondii, for cats with T. gondii antigen in aqueous humor and for cats with coronavirus antibody titers > or = 1:100. Aqueous humor IL-6 activity was greater than corresponding serum IL-6 activity in 21/27 cats. These results show that IL-6 is produced intraocularly in some cats with uveitis and that IL-6 may be a mediator of uveitis in cats.

Polymerase chain reaction for the detection of Toxoplasma gondii in aqueous humor of cats

OBJECTIVES

To develop Toxoplasma gondii B1 gene polymerase chain reaction (PCR) for use with aqueous humor of cats, and to report PCR and antibody detection results in naturally exposed cats with and without uveitis.

SAMPLE POPULATION

Serum and aqueous humor samples from client-owned, healthy cats (n = 23) and client-owned cats with uveitis (n = 43).

PROCEDURE

T gondii-specific IgM and IgG were measured in serum and aqueous humor from all cats. The Goldman-Witmer coefficient for ocular antibody production was calculated for cats positive for T gondii-specific IgM or IgG in aqueous humor. Aqueous humor from all cats was assessed by the B1 gene PCR.

RESULTS

T gondii was detected in aqueous humor by PCR from 2 of 23 (8.7%) healthy cats and 8 of 43 (18.6%) cats with uveitis. T gondii-specific IgM in either serum or aqueous humor was detected in 5 of 8 (62.5%) cats with uveitis and T gondii in aqueous humor. All cats with uveitis and T gondii in aqueous humor had anterior segment disease. In 5 of 8 (62.5%) cats with uveitis and T gondii in aqueous humor, ocular production of T gondii antibodies was not detected. T gondii was not detected in aqueous humor from 14 of 17 (82.4%) cats with ocular production of T gondii-specific antibody.

CONCLUSIONS

The presence of T gondii in aqueous humor may correlate to clinical disease in some, but not all, cats.

CLINICAL RELEVANCE

T gondii-specific aqueous humor antibody tests and PCR should be used together to aid in the diagnosis of ocular toxoplasmosis in cats.

Detection of Toxoplasma gondii-specific IgA in the aqueous humor of cats

Toxoplasma gondii-specific IgA, IgM, and IgG were measured by ELISA in the serum and aqueous humor of 29 client-owned cats with endogenous uveitis and 7 specific-pathogen-free cats tested sequentially for 20 weeks after inoculation with T gondii. Local antibody production in aqueous humor was estimated by multiplying the aqueous humor-to-serum T gondii-specific antibody ratio by the serum-to-aqueous humor total IgG (C value) or calicivirus-specific IgG (CTC value) ratio. Evidence for local production of antibody in aqueous humor was defined as C value greater than 8 or CTC value greater than 1. Toxoplasma gondii-specific IgM CTC values, IgG CTC values, or IgA CTC values greater than 1 were detected in the aqueous humor of 18 of 29 (62.1%) client-owned cats with endogenous uveitis; 2 cats had IgA CTC values greater than 1 without detectable IgM or IgG in aqueous humor. Toxoplasma gondii-specific IgM was not detected in the aqueous humor of experimentally inoculated cats before or after inoculation. Immunoglobulin G C values greater than 8 were detected in all 7 experimentally inoculated cats and ranged from 10.4 to 145.5. Immunoglobulin G C values greater than 8 were first detected 4 to 8 weeks after T gondii inoculation and were undetectable by week 16 after inoculation. Immunoglobulin A C values greater than 8 were detected in 4 of 7 cats and ranged from 12.7 to 264.3. Immunoglobulin A C values greater than 8 were first detected 4 to 8 weeks after inoculation, and were detected in 2 cats during week 20 after inoculation. It was concluded that some cats infected with T gondii develop detectable concentrations of T gondii-specific IgA in aqueous humor.

Detection of Toxoplasma gondii-specific IgA in the serum of cats

An ELISA for detection of Toxoplasma gondii-specific IgA in feline serum was developed. A group of cats (n = 7) was inoculated orally with T gondii bradyzoites. Toxoplasma gondii-specific serum IgM, IgG, and IgA responses were followed sequentially by use of the ELISA for 34 weeks. Serum IgA was detected later than IgM or IgG, and was detected in most cats on week 34 after inoculation. None of the cats was seropositive for IgA during the oocyst-shedding period. A group of client-owned cats with suspected clinical toxoplasmosis and a group of healthy cats were tested for T gondii-specific IgA in serum. A trend toward association of T gondii-specific IgA in serum of cats with ocular disease was observed.

Serologic prevalence of selected infectious diseases in cats with uveitis

Serologic evidence of infection by Toxoplasma gondii, feline leukemia virus, feline coronaviruses, or feline immunodeficiency virus (FIV) is commonly found in cats with uveitis. Serum samples from 124 cats with uveitis were assayed by use of ELISA for the detection of T gondii-specific immunoglobulin M (IgM), IgG, and circulating antigens (Ag), as well as an ELISA for feline leukemia virus Ag, an ELISA for antibodies to FIV, and an indirect fluorescent antibody assay for antibodies to feline coronaviruses. Serologic evidence of infection by 1 or more of the infectious agents was detected in 83.1% of the samples. Serologic evidence of T gondii infection, defined as the detection of T gondii-specific IgM, IgG, or Ag in serum, was found in 74.2% of the samples. The seroprevalence of T gondii infection was significantly greater in cats with uveitis than in healthy cats from a similar geographic area. Serum samples from cats with serologic evidence of both T gondii and FIV infections were more likely to contain T gondii-specific IgM without IgG than samples from cats with serologic evidence of T gondii infection alone. Cats with serologic evidence of FIV and T gondii coinfection had a higher T gondii-specific IgM titer geometric mean and a lower T gondii-specific IgG titer geometric mean than did cats with serologic evidence of T gondii infection alone. Serologic evaluation for T gondii infection should include assays that detect IgM, IgG, and Ag, particularly in cats coinfected with FIV.

Enzyme-linked immunosorbent assays for the detection of Toxoplasma gondii-specific antibodies and antigens in the aqueous humor of cats

Serum and aqueous humor samples, collected from 14 clinically normal cats and 96 cats with clinical evidence of intraocular inflammation, were assayed with ELISA for Toxoplasma gondii-specific immunoglobulin M (IgM), T gondii-specific IgG, T gondii-specific antigens, total IgG, and total IgM. Additionally, serum was assayed with ELISA for feline leukemia virus p27 antigen and antibodies against the feline immunodeficiency virus as well as with an immunofluorescent antibody assay for antibodies against feline coronaviruses. Calculation of the Goldmann-Witmer coefficient (C-value) for the T gondii-specific antibodies detected in aqueous humor established the likelihood of local antibody production. Serologic evidence of present or prior infection by an infectious agent was found in 81.9% of the clinically affected cats from which serologic results were available (77/94 cats). Seropositive results for toxoplasmosis were found in 74.0% of the clinically affected cats. Anterior segment inflammation was found in 93.1% (81/87 cats from which information was available) of the clinically affected cats, most of which were older males. Toxoplasma gondii-specific antibodies were not detected in the aqueous humor of 6 seropositive, clinically normal cats. The C-values for aqueous T gondii antibodies were greater than 1 in 44.8% of the cats and greater than 8 in 24.0% of the cats. Response to treatment with clindamycin HCl was positive in 15/20 (75%) of the T gondii-seropositive, clinically affected cats treated with this drug. In 13/15 (86.7%) T gondii-seropositive, clinically affected cats having a C-value greater than 1, response to treatment with clindamycin HCl was positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Ocular toxoplasmosis in wallabies (Macropus rufogriseus)

We initiated a pathologic investigation of ocular disease in wallabies. Of 21 animals examined, the eyes were investigated histologically in 11; in four of these animals the brains were also available for section and the sera were investigated in three. In ten animals only sera were received. Histologic studies showed bilateral or unilateral cataract in five animals. Eight animals, with or without cataracts, showed various degrees of keratitis, uveitis, choroidoretinitis, or endophthalmitis. In three animals Toxoplasma cysts were found within the retina or brain, or both. Of the 13 cases examined serologically 11 were positive for toxoplasmosis; three reached high titers.