Paragonimus kellicotti infection in wild carnivores in southwestern Ontario: II. Histopathologic features.

Pulmonary lesions associated with naturally acquired Paragonimus kellicotti infection were studied in mink (Mustela vison), striped skunks (Mephitis mephitis), red foxes (Vulpes vulpes) and a coyote (Canis latrans). In ,ink a fibrous capsule was formed around mature flukes in dilated bronchioles or bronchi, and there was mild focal interstitial pneumonitis adjacent to fluke eggs in alveoli and migrating parasites. A thick wall, infiltrated heavily with mononuclear cells and eosinophils, surrounded mature P. kellicotti in skunks and an extensive inflammatory reaction was found around fluke eggs. In red foxes the wall was thin, hemorrhagic and contained little collagen; necrosis was associated with migrating parasites. Thick capsules formed by marked fibroplastic changes in the lamina propria of affected bronchi were found in the coyote. In raccoons with pleural adhesions massive fibroplasia with eosinophil infiltration beneath the pulmonary pleura suggested a reaction to a migrating parasite entering the lung from the thoracic cavity. It was thought that immature P. kellicotti may have caused the lesion.     

Humoral factors and nonspecific immune suppression in Syrian hamsters infected with Leishmania donovani

Leishmania donovani produces progressive wasting and ultimately fatal visceral leishmaniasis in Syrian hamsters and provides an excellent model of progressive disease in humans. Experimentally infected hamsters were used to investigate the development of nonspecific immune suppression during visceral leishmaniasis and its association with humoral factors and wasting. At 2 wk all infected hamsters had developed antibody against a 59-kDa parasite antigen not recognized by sera of control hamsters. By 4 wk, strong antibody responses were noted against antigens of 26, 35, 46, 69, 107, and 120 kDa. No additional antigen was recognized at 6 or 8 wk or in hamsters treated with high doses of a pentavalent antimonial (stibogluconate sodium, 100 mg/kg/day for 5 days). Weight loss was first noted in infected hamsters at 8 wk. No difference in splenic lymphocyte proliferation in response to concanavalin A (Con A) was noted at 2 wk, but by 6 wk infected animals had only 20% of the Con A response of controls, and by 8 wk only 13%. Furthermore, incubation of splenic lymphocytes from uninfected control animals with 5% fetal calf serum and 5% serum from infected hamsters obtained at 4, 6, or 8 wk suppressed Con A responses by 50%, 99%, and 100%, respectively. Spleen cells from drug-treated animals exhibited no suppression of Con A responses when incubated with 5% autologous serum, but there was profound suppression when they were incubated with 5% autologous serum obtained during the acute phase of infection. Humoral factors, but not wasting, contributed to the suppression of lymphocyte responses.     

The American lung fluke, Paragonimus kellicotti, in a cat model

Twenty-four specific-pathogen-free domestic cats were infected orally with from 2 to 30 Paragonimus kellicotti metacercariae and followed for 2-61 wk. Following infection by metacercarial cysts dissected from crayfish, the lungs of the cats undergo changes of intense eosinophilic pneumonia, granulomatous pneumonitis, squamous epithelial-lined cyst formation of bronchogenic origin, and finally (late in infection) partial resolution of the host response. Bronchograms and mechanical probing illustrate the patency of cyst communication with bronchi. The modulation of the host response and adaptive changes in the host lung tissue are seen late in infection and have previously been unreported or underemphasized. These adaptive responses may account for the number of asymptomatic cases accidentally found in veterinary patients and the difficulty in prompt and proper diagnosis in human cases.     

Timing of birth in Syrian hamsters.

The effects of mating time and of LD cycles on the timing of birth and length of gestation were examined in Syrian hamsters (Mesocricetus auratus). Hamsters maintained on 14L:10D cycles were mated for 2 h either in the evening or in the morning, and groups of hamsters mated in the morning were subjected to either a 6-h advance shift or a 6-h delay shift of the LD cycle on Days 5-14 of gestation. For the last 2 days of gestation the hamsters were kept in constant dim light and observed every hour to determine the time of birth. Hamsters mated in the evening gave birth an average of 4.8 h before those mated in the morning, and the hamsters subjected to an advance shift gave birth an average of 8.1 h before those subjected to delay shift. The results show that 80-100% of births occur during the subjective day on Day 16 of gestation and that the minimum duration of gestation is 15 days and 2 h. The regulation of birth appears to involve two processes, an interval timer related to the time of conception and a circadian rhythm that is governed by the LD cycle.     

Ultrastructural and immunohistochemical analysis of cholangiocarcinoma in immunized Syrian golden hamsters infected with Opisthorchis viverrini and administered with dimethylnitrosamine.

Utilizing the experimental model in Syrian golden hamsters, we explored the role of immunization in carcinogenesis. The animals, which were infected with liver flukes (Opisthorchis viverrini), and administered a subcarcinogenic dose of dimethylnitrosamine, developed cancer. Pre-immunizing with a crude somatic antigen did not reduce cancer development, but accelerated carcinogenesis. Histopathological analysis of the cancer tissues was done once at week 30 and again at week 39 using H and E staining, immunostaining for the p53 tumor suppressor phosphoprotein, and electron microscopy. Thirty weeks after immunization, the immunized hamsters developed tubular adenocarcinoma at a higher rate (71.43%) than the non-immunized group (20.00%). This rate (20.00%) increased to 63.64% by week 39. The small foci cancer in the non-immunized group decreased in frequency from 80.00% (at week 30) to 36.36% (by week 39), suggesting the small foci cancer progressed to tubular adenocarcinoma during the 9-week interval. Most of the observed tubular adenocarcinoma was well differentiated. Nearly all hamsters that tested positive for cancer also tested positive for p53 immunostaining in the epithelia of the small bile ducts. The positive reaction for p53-immunostaining was localized in the rough endoplasmic reticulum, Golgi apparatus and perinuclear membranes. The electron micrographs of these positive p53-immunostained cells showed characteristics of early cancer. The detection of p53 in early cancer development makes it a candidate as a tumor marker.     

Laboratory assessment of chronic hepatitis in Syrian hamsters.

Clinical chemistry studies in the diagnosis of hamster diseases have received little attention. Although normal values exist for serum constituents, the effects of disease on these values are not well documented. Chronic hepatitis is endemic in several Syrian hamster (Mesocricetus auratus) colonies and is reported mainly through routine histologic examination. We investigated whether any differences in serum clinical chemistries were present in animals with hepatobiliary disease versus unaffected hamsters. Only serum alanine aminotransferase (ALT) and bile acids were significantly elevated in hamsters with chronic hepatitis only. In hamsters that had both chronic hepatitis and biliary disease, the serum ALT, alkaline phosphatase, cholesterol, and bile acids were significantly elevated. The results of this study indicated that serum clinical chemistries may be a useful antemortem diagnostic test for chronic hepatobiliary disease in hamsters.     

Clostridium difficile typhlitis associated with cecal mucosal hyperplasia in Syrian hamsters.

A sudden increase in mortality occurred in a closed breeding colony of Syrian hamsters (Mesocricetus auratus). The colony consisted of approximately 40 hamsters, 8 of which were affected. Four adult males died suddenly. One pregnant female and one weanling died after having been observed as depressed for 1 day and 2 weeks respectively. One weanling and one adult male were euthanized. All affected hamsters had signs of diarrhea. At necropsy, hemorrhagic fluid-filled ceca were noted in five of eight animals. Clostridium difficile cytotoxin B was present in high titers [10(-3) to 10(-8)] in cecal contents of six of six animals tested, whereas C. difficile culture yielded positive results in only one of six animals. Histopathologically, findings consistent with Clostridium-induced typhlitis including necrosis, epithelial denudation, vascular congestion, and hemorrhage were present in six of six ceca evaluated. In addition, signs of a more chronic disease process included cecal mucosal hyperplasia in five of six hamsters. A silver stain of cecal hyperplastic mucosa for intracellular organisms including Campylobacter-like organisms was negative in all affected hamsters. Antibiotics had not been administrated to any hamster in this colony, nor had the affected animals been experimentally manipulated. Testing for antibiotic residues in the feed was negative, and C. difficile was not isolated from feed, water, or feces of unaffected hamsters. Thus C. difficile-induced typhlitis should be included in the differential diagnosis of deaths in hamsters which have no clinical histories of prior antibiotic administration or experimental manipulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pheromone-induced anorexia in male Syrian hamsters

Transition from long days (LDs) to short days (SDs) triggers seasonal obesity in Syrian hamsters. We report here that SD-exposed males housed near females exhibit obesity resistance, episodic weight loss, and reduced adiposity. Negative energy balance is achieved by reduced eating, elevated motor activity, and increased caloric efficiency without metabolic compensation. Circulating leptin, insulin, testosterone, corticosterone, and cortisol are normal or reduced in obesity-resistant hamsters. When males are housed in chambers that block physical, visual, and auditory, but not pheromonal, signals from females, resistance to seasonal obesity persists. Moreover, inhalation of extracts from pheromone-releasing flank glands of females suppresses eating and weight gain in SD-exposed males. This novel phenomenon, pheromone-induced anorexia, shows that female pheromones play a critical role in the seasonal energy balance of male hamsters. These findings provide a model to study neural and endocrine mechanisms that underlie eating disorders.     

ELISA of rat sera infected with Paragonimus iloktsuenensis

Enzyme-linked immunosorbent assay (ELISA) of paragonimiasis iloktsuenensis rat sera was performed using crude antigens of Paragonimus iloktsuenensis (PIA), P. westermani (PWA) and Clonorchis sinensis (CSA). Three crude antigens (PIA, PWA, CSA) were prepared to saline homogenated supernatants of whole adult worms. Infected rat sera were obtained biweekly from the albino rats fed 50-80 metacercariae of P. iloktsuenensis through gastric catheter. Experimental groups were divided into 4 groups: GI (controls), GII, GIII and GIV according to 1-7 worms as GII, 10-19 worms as GIII and 22-40 worms as GIV, respectively. In ELISA, the mean OD values of each group for the homologous antigen (PIA) were increased significantly compared to the control sera at the 4th week of infection. With the progress of duration of infection, the mean OD values of infected sera of GII & GIV continuously increased up to the 12th week (last week), but in GIII the mean OD value increased until the 10th week. No significance was noted among the infection dose groups (GII, GIII and GIV), after the 6th week of infection. Also, the OD values of all infected rats did not show any proportional relationships to the number of worms recovered. In brief, the antibody productivity of individual rats were strongly different. The rat sera infected with P. iloktsuenensis cross-reacted with those infected with P. westermani or C. sinensis, as identified by OD values.     

Immunologic studies on hamsters infected with Entamoeba histolytica.

The serologic and cell-mediated immune responses of hamsters exposed to 2 strains of Entamoeba histolytica (HM-1 and HM-19) were evaluated by a series of in vitro tests. The pathogenicity of the 2 strains was evaluated in terms of their ability to produce liver abscesses and spleen enlargement. Antibody response was evaluated by the indirect hemagglutination test. The cellular immune response was assayed by increased DNA synthesis by lymphocytes and migration inhibition of macrophages.     

Serum IgE levels in rats infected with Paragonimus westermani]

Paragonimus westermani is a common fluke in Korea. The present study aimed to determine serum total IgE and specific IgG levels in experimental paragonimiasis of rats. Each Wistar rat was inoculated orally with 20-25 metacercariae of P. westermani from Cambaroides similis. Before and after infection (1, 2, 3, 4, 6, 8 weeks) of P. westermani, the blood was collected from the retro-orbital venous plexus of rats and kept serum at -70 degrees C. Serum total IgE and specific IgG levels were determined by the capture and conventional enzyme-linked immunosorbent assay, respectively. The results were as follows; 1. Serum IgE values were increased to 0.18 +/- 0.042 at 2 weeks, 0.28 +/- 0.151 at 4 weeks and 0.43 +/- 0.055 at 8 weeks after infection. The absorbances of non-infected rats ranged 0.07 +/- 0.021-0.12 +/- 0.025. 2. Specific IgG values were slightly increased at 3 weeks (0.20 +/- 0.032) and gradually increased up to 8 weeks (0.31 +/- 0.067) after infection. The absorbances of non-infected rats ranged 0.11 +/- 0.035-0.18 +/- 0.019. The present results suggested that P. westermani could elevate serum IgE and specific IgG antibodies in Wistar rats which were not a good definitive host.     

Bicuculline blocks diazepam-induced feeding in Syrian hamsters

Bicuculline antagonizes diazepam induced feeding in Syrian hamsters in a dose dependent manner using doses which do not affect running wheel activity. These results suggest that diazepam-induced feeding can be completely and specifically blocked by antagonizing GABA.