Spatial and seasonal factors are key determinants in the aggregation of helminths in their definitive hosts: Pseudamphistomum truncatum in otters (Lutra lutra).

Parasites are typically aggregated within their host populations. The most heavily infected hosts are frequently cited as targets for optimal disease control. Yet a heavily infected individual is not necessarily highly infective and does not automatically contribute a higher proportion of infective parasitic stages than a host with fewer parasites. Here, Pseudamphistomum truncatum (Opisthorchiida) parasitic infection within the definitive otter host (Lutra lutra) is used as a model system. The hypothesis tested is that variation in parasite abundance, aggregation and egg production (fecundity, as a proxy of host infectivity) can be explained by abiotic (season and region) or biotic (host age, sex and body condition) factors. Parasite abundance was affected most strongly by the biotic factors of age and body condition, such that adults and otters with a higher condition index had heavier infections than sub-adults or those with a lower condition index, whilst there were no significant differences in parasite abundance among the seasons, regions (ecological regions defined by river catchment boundaries) or host sexes. Conversely, parasite aggregation was affected most strongly by the abiotic factors of season and region, which were supported by four different measures of parasite aggregation (the corrected moment estimate k, Taylor's Power Law, the Index of Discrepancy D, and Boulinier's J). Pseudamphistomum truncatum was highly aggregated within otters, with aggregation stronger in the Midlands (England) and Wales than in the southwestern region of the United Kingdom. Overall, more parasites were found in fewer hosts during the summer, which coincides with the summer peak in parasite fecundity. Combined, these data suggest that (i) few otters carry the majority of P. truncatum parasites and that there are more infective stages (eggs) produced during summer; and (ii) abiotic factors are most influential when describing parasite aggregation whilst biotic factors have a greater role in defining parasite abundance. Together, parasite abundance, aggregation and fecundity can help predict which hosts make the largest contribution to the spread of infectious diseases.

The relative importance of host characteristics and co-infection in generating variation in Heligmosomoides polygyrus fecundity.

We examined the relative importance of intrinsic host factors and microparasite co-infection in generating variation in Heligmosomoides polygyrus fecundity, a parameter that serves as a proxy for infectiousness. We undertook extensive trapping of Apodemus flavicollis, the yellow-necked mouse in the woodlands of the Italian Alps and recorded eggs in utero from the dominant nematode species H. polygyrus, and tested for the presence of five microparasite infections. The results showed that sex and breeding status interact, such that males in breeding condition harboured more fecund nematodes than other hosts; in particular, worms from breeding males had, on average, 52% more eggs in utero than worms from non-breeding males. In contrast, we found a weak relationship between intensity and body mass, and no relationship between intensity and sex or intensity and breeding condition. We did not find any evidence to support the hypothesis that co-infection with microparasites contributed to variation in worm fecundity in this system. The age-intensity profiles for mice singly-infected with H. polygyrus and those co-infected with the nematode and at least one microparasite were both convex and not statistically different from each other. We concluded that intrinsic differences between hosts, specifically with regard to sex and breeding condition, contribute relatively more to the variation in worm fecundity than parasite co-infection status.

The effects of social structure and sex-biased transmission on macroparasite infection.

Mathematical models of disease dynamics tend to assume that individuals within a population mix at random and so transmission is random, and yet, in reality social structure creates heterogeneous contact patterns. We investigated the effect of heterogeneity in host contact patterns on potential macroparasite transmission by first quantifying the level of assortativity in a socially structured wild rodent population (Apodemus flavicollis) with respect to the directly-transmitted macroparasitic helminth, Heligmosomoides polygyrus. We found the population to be disassortatively mixed (i.e. male mice mixing with female mice more often than same sex mixing) at a constant level over time. The macroparasite H. polygyrus has previously been shown to exhibit male-biased transmission so we used a Susceptible-Infected (SI) mathematical model to simulate the effect of increasing strengths of male-biased transmission on the prevalence of the macroparasite using empirically-derived transmission networks. When transmission was equal between the sexes the model predicted macroparasite prevalence to be 73% and infection was male biased (82% of infection in the male mice). With a male-bias in transmission ten times that of the females, the expected macroparasite prevalence was 50% and was equally prevalent in both sexes, results that both most closely resembled empirical dynamics. As such, disassortative mixing alone did not produce macroparasite dynamics analogous to those from empirical observations; a strong male-bias in transmission was also required. We discuss the relevance of our results in the context of network models for transmission dynamics and control.

Hantavirus and arenavirus antibody prevalence in rodents and humans in Trentino, Northern Italy.

The spatial and temporal distribution of hantavirus and arenavirus antibody-positive wild rodents in Trentino, Italy, was studied using immunofluorescence assays (IFA) in two long-term sites trapped in 2000-2003, and six other sites trapped in 2002. The overall hantavirus seroprevalence in the bank voles, Clethrionomys glareolus (n=229) screened for Puumala virus (PUUV) antibodies was 0.4%, and that for Apodemus flavicollis mice (n=1416) screened for Dobrava virus (DOBV) antibodies was 0.2%. Antibodies against lymphocytic choriomeningitis virus (LCMV) were found in 82 (5.6%) of the 1472 tested rodents; the seroprevalence being 6.1% in A. flavicollis (n=1181), 3.3% in C. glareolus (n=276), and 14.3% in Microtus arvalis (n=7). Of the serum samples of 488 forestry workers studied by IFA, 12 were LCMV-IgG positive (2.5%) and one DOBV-IgG positive (0.2%), however, the latter could not be confirmed DOBV-specific with a neutralization assay. Our results show a widespread distribution but low prevalence of DOBV in Trentino, and demonstrate that the arenavirus antibodies are a common finding in several other rodent species besides the house mouse.

Iliofemoral deep vein thrombosis: conventional therapy versus lysis and percutaneous transluminal angioplasty and stenting.

OBJECTIVE: To compare conventional treatment (heparin and warfarin) of iliofemoral venous thrombosis with multimodality treatment (lysis and stenting). SUMMARY BACKGROUND DATA: Several studies have reported on conventional therapy for iliofemoral venous thrombosis with disappointing results. However, more recent studies have reported better results with multimodality treatment. METHODS: Fifty-one consecutive patients with extensive iliofemoral venous thrombosis were treated during a 10-year period. If there were no contraindications, patients were given the option to choose between conventional therapy (group 1) and multimodality therapy (group 2). The multimodality treatment strategy included catheter-directed lysis followed by percutaneous transluminal balloon angioplasty (PTA) and stenting for residual iliac stenoses. All patients underwent routine venous duplex imaging at 30 days, 3 months, 6 months, and every 6 months thereafter. RESULTS: There were 33 patients in group 1 and 18 patients in group 2. Demographic and clinical characteristics were comparable for both groups. Initial lysis was achieved in 16 of 18 patients (89%) in group 2. Ten of 18 patients in group 2 had residual stenosis after lysis (8 primary and 2 secondary to malignancy), and they were treated with PTA/stenting with an initial success rate of 90%. Two patients in group 1 (6%) had a symptomatic pulmonary embolism (none in group 2). At 30 days, venous patency and symptom resolution were achieved in 1 of 33 patients (3%) in group 1 versus 15 of 18 (83%) in group 2. Kaplan-Meier analysis showed primary iliofemoral venous patency rates at 1, 3, and 5 years of 24%, 18%, and 18% and 83%, 69%, and 69% for groups 1 and 2, respectively. Long-term symptom resolution was achieved in 10 of 33 patients (30%) in group 1 versus 14 of 18 (78%) in group 2. Kaplan-Meier life table analysis showed similar survival rates at 1, 3, and 5 years of 100%, 93%, and 85% for group 1 and 100%, 93%, and 81% for group 2. CONCLUSIONS: Lysis/stenting treatment was more effective than conventional treatment in patients with iliofemoral vein thrombosis.

Ultrasound: impact on diagnostic peritoneal lavage, abdominal computed tomography, and resident training.

Our objective was to determine the impact of abdominal ultrasound (US) on 1) the use of diagnostic peritoneal lavage (DPL) and abdominal computed tomography (ACT) for diagnosing blunt abdominal trauma (BAT) and on 2) surgical resident training. The study design was a retrospective chart review. Patients sustaining BAT who had ACT or DPL done during the 1-year period before the introduction of US (pre-US) were compared with those from a 1-year period beginning 6 months after US (post-US). Data collected included diagnostic modality, demographic data, mortality, associated injuries, length of stay, mechanism of injury, and number of exploratory laparotomies. Of 128 patients in the pre-US group, 35 patients (27%; P < 0.001) underwent DPL, 0 patients (0%; P < 0.001) received US, and 92 patients (72%) received ACT, with positive results for 31 patients (34%). Exploratory laparotomy was performed on 35 patients (27%) in the pre-US group. Of 140 patients in the post-US group, 8 patients (6%; P < 0.001) underwent DPL, 120 patients (85%; P < 0.001) received US, and 108 patients (77%) received ACT, with positive results for 44 patients (42%). Exploratory laparotomy was performed on 22 patients (15%; P < 0.001) in the post-US group. Resident experience with DPL before and after the introduction of US and availability of US for graduated residents was documented. Chi-square and Fisher's exact test were used for statistical analysis. Resident experience changed from 22 to 3 DPLs per year in the pre- and post-US groups, respectively. Ten per cent of graduating residents had US available for use after leaving this institution. US replaced DPL and resulted in slightly more positive ACT scans in assessing BAT at our institution. Paradoxically, only 10 per cent of graduating residents had US available after leaving this institution. Until the use of US for diagnosing BAT has widespread use in the community, we must question our adequacy of resident preparation for diagnosing BAT.

Experimental infection in cats with a cagA+ human isolate of Helicobacter pylori.

BACKGROUND: Helicobacter pylori has been cultured from the inflamed gastric mucosa of naturally and experimentally-infected cats. The lesions in the H. pylori-infected cat stomach mimic many of the features seen in human stomachs infected with H. pylori. This study sought to determine whether H. pylori-negative, specific pathogen-free cats with normal gastric mucosa were susceptible to colonization with a human cagA+ strain of H. pylori, and whether gastritis developed after infections. METHODS: Four H. pylori-negative cats treated with cimetidine were orally dosed 3 times at 2-day intervals with 3 ml (1.5 x 108 CFU/ml) of H. pylori. RESULTS: All experimentally-infected cats became persistently colonized as determined by H. pylori isolation from gastric tissue by culture at 12 weeks, and all 4 cats were found positive by PCR during serial gastric biopsies and necropsy at 15 weeks postinoculation. The 2 control cats did not have H. pylori isolated, nor was gastric tissue positive by PCR. The H. pylori isolated from the 4 experimentally-infected cats had RFLP patterns specific for the flaA gene identical to those of the inoculating strain. All 4 H. pylori-infected cats had multifocal gastritis, consisting of lymphoid aggregates plus multiple large lymphoid nodules. In the control cats, one cat had a few focal lymphocytic aggregates in the body submucosa, whereas the second cat had normal gastric mucosa. CONCLUSION: Human cagA+ H. pylori readily colonized the cat stomach and produced a persistent gastritis. The findings demonstrate the utility of the cat to study H. pylori induced pathogenesis.

Proliferative enteropathy of rabbits: the intracellular Campylobacter-like organism is closely related to Lawsonia intracellularis.

The intracellular Campylobacter-like organism associated with proliferative enteropathy of rabbits is closely related to Lawsonia intracellularis, the primary pathogen in porcine intestinal adenomatosis. Polymerase chain reaction primers based on the 16S rRNA gene of L. intracellularis were used to amplify DNA harvested from intestinal tissues of rabbits with severe proliferative intestinal lesions containing curved argentophilic intracellular bacteria. Sequencing of a 180-nucleotide DNA fragment of the 550-base pair-amplified polymerase chain reaction product revealed >98% similarity between the organism associated with the rabbit disease and the homologous sequence found in L.intracellularis.

Use of PCR and culture to detect Helicobacter pylori in naturally infected cats following triple antimicrobial therapy.

Helicobacter pylori causes gastritis and peptic ulcers and is linked to gastric cancer. Domestic cats from a commercial source were found to be naturally infected with H. pylori, and studies were undertaken to eradicate H. pylori from infected cats by using triple antimicrobial therapy. Eight cats infected with H. pylori were used in the study. Six cats received a 21-day course of oral amoxicillin, metronidazole, and omeprazole, and two cats served as controls. Two weeks and 4 weeks posttreatment (p.t.), all six treated cats were negative at several sites (saliva, gastric juice, and gastric mucosa) for H. pylori by culture. However, as determined by PCR with primers specific for the 26-kDa product, the majority of cats at 2 and 4 weeks p.t. had gastric fluid samples which were positive for H. pylori and three of three cats at 2 weeks p.t. had dental plaque which was positive for H. pylori. At 6 weeks p.t., all six cats had H. pylori-negative cultures for samples from several gastric sites taken at necropsy, and only one cat had H. pylori cultured from gastric juice. PCR analysis revealed that five of six cats had H. pylori DNA amplification products from plaque, saliva, and/or gastric fluid samples. Negative bacterial cultures for cats for which there was demonstrable PCR amplification of H. pylori DNA may reflect the inability of in vitro culture techniques to isolate small numbers of H. pylori organisms, focal colonization at sites not cultured, or a failure of the antibiotics to successfully eradicate H. pylori from extragastric sites which allowed subsequent recolonization of the stomach after cessation of therapy. Alternatively, the treatment strategy may have induced in vivo viable but nonculturable coccoid forms of H. pylori. The H. pylori cat model should allow further studies to test these hypotheses as well as the efficacies of other combined therapeutic regimens. Also, because 100% of these cats were naturally infected with H.pylori, this model should prove useful in exploring mechanisms whereby human populations in underdeveloped countries, which have H. pylori infection rates approaching 100%, have a high rate of recurrence of H. pylori infection after use of prescribed antibiotic therapies that successfully eradicate H. pylori in individuals in developed countries.

Helicobacter mustelae-associated hypergastrinemia in ferrets (Mustela putorius furo).

OBJECTIVE: To determine whether ferrets naturally infected with Helicobacter mustelae were hypergastrinemic, compared with ferrets that were specific-pathogen-free (SPF) for H mustelae. DESIGN: Plasma gastrin concentrations in H mustelae-infected and SPF ferrets were measured at 3 time points and compared to determine whether H mustelae was associated with hypergastrinemia. ANIMALS: 21 H mustelae-infected ferrets and 10 SPF ferrets. PROCEDURE: The H mustelae status of the ferrets was confirmed prior to commencement of the study. Gastric endoscopy was used to obtain gastric mucosal pinch biopsy specimens that were processed for rapid-urease assay, microaerophilic culturing, and histologic evaluation. Plasma gastrin concentrations were determined at 3 time points: baseline after a 12-hour nonfeeding period, and 30 and 60 minutes after oral administration of a standardized meal. Gastrin was measured by radioimmunoassay. RESULTS: The results for the H mustelae-infected group (mean +/- SEM pg/ml) were: baseline, 54.4 +/- 2.56; 30 minutes, 94.5 +/- 6.05; and 60 minutes, 82.6 +/- 5.73. The SPF group results were: baseline, 55.8 +/- 7.35; 30 minutes, 80.8 +/- 5.77; and 60 minutes, 59.7 +/- 4.95. There was a significant (P < 0.01) difference at the 60-minute time point between the 2 groups of animals. The H mustelae group had a 17% higher mean gastrin value at 30 minutes. CONCLUSIONS: Helicobacter mustelae is associated with hypergastrinemia in ferrets. CLINICAL RELEVANCE: Helicobacter-induced hypergastrinemia may be related to the pathogenesis of peptic ulcer disease in ferrets.

Eosinophil granulocytic sarcoma in a New Zealand white rabbit.

An 18-month-old New Zealand White rabbit developed a rapidly growing firm perianal mass. Within 2 months, the mass increased in size from 4.0 x 2.0 cm to 7.5 x 7.0 x 3.5 cm. Cut surfaces of the mass were white to yellow with foci of hemorrhage. Histopathologic examination revealed neoplastic granulocytes that invaded the dermis of the overlying skin, subcutaneous tissue, and the regional skeletal muscle. The tumor was comprised of myeloid cells with large eosinophilic cytoplasmic granules that had the histochemical and ultrastructural features of eosinophils. This is the first report of an eosinophil granulocytic sarcoma in lagomorphs.

Detection of Clostridium difficile toxins from the small intestine and cecum of rabbits with naturally acquired enterotoxemia.

Four specific-pathogen-free rabbits with anorexia died peracutely; decreased fecal output, nasal exudate, and labored breathing were the only other clinical abnormalities observed in two of the rabbits before death. The animals, three juveniles and one adult, were on a standard polyclonal antibody production regimen and had received immunizations approximately 2 weeks before presentation. External examination revealed distended abdomen and perineal fecal staining. At necropsy the small intestine was distended with fluid, and the cecum was distended with chyme. The small intestines and cecum had marked serosal hyperemia. Anaerobic bacterial culture techniques were used to isolate Clostridium difficile from the small intestine (3/4) and cecum (2/4). In all cases C. difficile toxin B was detected at high titers (10(2) to > 10(5)) in the small intestine by cytotoxicity assay with HeLa 229 cell culture. In two of the four rabbits C. difficile was isolated, and cytotoxin titers were detected at 10(1) and 10(4) in the cecum of affected rabbits. Toxin B was neutralized with C. sordellii antiserum but not C. spiroforme antiserum. In addition, toxin A was detected in each of the cytotoxin B-positive samples by a commercial toxin A enzyme immunosorbent assay. In vitro production of toxins A and B was detected from each culture isolate after incubation in chopped meat broth. These cases are noteworthy because spontaneous (nonantibiotic-associated) C. difficile enterotoxemia has not been previously reported in rabbits. Also the toxins of clostridial organisms are usually documented in the cecum, not the small intestine, of rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Patience with patients: a must for outpatient labs.

It's the little things that make a big difference in how outpatients perceive their care and ultimately determine whether they will return for future services. Here's a light-hearted look at some outpatients who may seem all too familiar.