Host factors associated with the detection of Aeromonas salmonicida and Yersinia ruckeri in Ontario, Canada government fish hatcheries

This paper presents an epidemiological investigation of Ontario Ministry of Natural Resources Fish Health Laboratory data from 1981 to 1997, to determine whether fish species and age were associated with lot-level detection of Aeromonas salmonicida and Yersinia ruckeri in hatchery fish. In stepwise logistic regression, the species brook trout and back-cross (lake trout crossed with the hybrid “splake”) were more likely to test A. salmonicida-positive compared to all other species reared in the hatcheries. Similarly, the species brook trout was significantly more likely to test Y. ruckeri-positive compared to all other species. For both pathogens, the 1–5-month age group was associated significantly with detection. These findings suggest that purposive sampling of higher-risk fish lots could increase the likelihood of detecting both study pathogens.     

Molecular screening and risk factors of enterotoxigenic Escherichia coli and Salmonella spp. in diarrheic neonatal calves in Egypt

The aim of the present study was to carry out molecular epidemiological investigation on enterotoxigenic Escherichia coli (ETEC) K99 and Salmonella spp. in diarrheic neonatal calves. Fecal samples were obtained from 220 diarrheic calves at 9 farms related to four governorates in central and northern Egypt. E. coli and Salmonella spp. isolates were examined for E. coli K99 and Salmonella spp. using PCR. ETEC K99 was recovered from 20 (10.36 %) out of 193 isolates, whereas Salmonella spp. was recovered from nine calves (4.09%).Multivariable logistic regression was used to evaluate the risk factors associated with both infections. ETEC K99 was significantly affected by age (P < 0.01; OR: 1.812; CI 95%: 0.566–1.769), colostrum feeding practice (P < 0.01; OR: 5.525; CI 95%: 2.025–15.076), rotavirus infection (P < 0.001; OR: 2.220; CI 95%: 0.273–1.251), vaccination of pregnant dams with combined vaccine against rotavirus, coronavirus and E. coli (K99) (P < 0.001; OR: 4.753; CI 95%: 2.124–10.641), and vitamin E and selenium administration to the pregnant dam (P < 0.01; OR: 3.933; CI 95%: 0.703–1.248).Infection with Salmonella spp. was found to be significantly affected by the animal age (P < 0.05; OR: 0.376; CI 95%: 0.511–1.369), Hygiene (P < 0.05; OR: 0.628; CI 95%: 1.729–5.612), and region (P < 0. 01; OR: 0.970; CI 95%: 0.841–1.624).The results of the present study indicate the importance of PCR as rapid, effective and reliable tool for screening of ETEC and Salmonella spp. when confronted with cases of undifferentiated calf diarrhea. Moreover, identification of the risk factors associated with the spreading of bacteria causing diarrhea may be helpful for construction of suitable methods for prevention and control.     

Prevalence and age-related infection of Cryptosporidium suis, C. muris and Cryptosporidium pig genotype II in pigs on a farm complex in the Czech Republic

A total of 413 pig faecal samples were collected from pre-weaners (119), starters (131), pre-growers (123) and sows (40) from a farm with a closed breeding system segmented into two breeding complexes and a growing complex in the region of Vysočina, Czech Republic and screened for the presence of Cryptosporidium using staining methods and genotyping (SSU rRNA). Cryptosporidium oocysts were detected by microscopy in the faeces of 21.1% of the samples (87/413). Sequence analyses and RFLP identified C. suis in 44, Cryptosporidium pig genotype II in 23 and C. muris in 2 samples. No mixed infections were found.Pigs under 7 weeks of age were infected with C. suis only. Cryptosporidium pig genotype II was found in animals from 7 weeks of age. No relationship was found between diarrhoea and any Cryptosporidium infection in any of the different age groups (P < 0.05). The pre-weaned pigs shed significantly more Cryptosporidium oocysts than older pigs and it was associated with C. suis infection.     

Life-history parameters of Culicoides (Avaritia) imicola Kieffer in the laboratory at different rearing temperatures

This laboratory study investigates the sub-adult developmental cycle of field collected Culicoides (Avaritia) imicola Kieffer (Diptera; Ceratopogonidae). The period required from blood-feeding field-collected females to the production of progeny adults occupied 34–56 days at 20 °C, 15–21 days at 25 °C and 11–16 days at 28 °C, demonstrating clear temperature dependence. When reared at 28 °C, C. imicola demonstrated higher variability in fecundity (between 2.4 and 20.6 eggs/female) and lower hatching rates (50.0–62.2%), although larval survival rates to pupation were low at all temperatures (20–30%). Similarly, the mean emergence rate from pupae was the highest at lower temperatures. These results highlight the difficulty in establishing and maintaining a laboratory colony of this species from field-collected material and results are discussed in reference to future research directions that may aid this process.     

Natural infection by Cryptosporidium sp., Giardia sp. and Eimeria leuckarti in three groups of equines with different handlings in Rio de Janeiro, Brazil

To detect Cryptosporidium sp., Giardia sp. and Eimeria leuckarti in horses, fecal samples were collected from three different handling horse groups from the state of Rio de Janeiro, Brazil. Group A was composed of “Mangalarga Marchador” pure breed horses, Group B was formed by horses of a Military Corporation and Group C by stray horses captured by the Center of Zoonosis Control Paulo Dacorso Filho. A total of 396 fecal samples were collected, 212 samples from Group A, 154 samples from Group B and 30 from Group C. The material was submitted to the centrifugation - flotation technique and staining by the safranin-methylene blue technique and analyzed. Oocysts of Cryptosporidium sp. were identified in 0.75% of the samples (n = 3); cysts of Giardia sp. in 0.5% (n = 2) and oocysts of E. leuckarti in 0.5% (n = 2). One case of E. leuckarti in group A and one of Cryptosporidium sp. in group B were observed. In group C were observed two cases of Cryptosporidium, two of Giardia and one of E. leuckarti,. Horses of group C were more parasitized by the three protozoans than animals from the other groups (p < 0.01). It was possible to verify that factors related to the animals, like host individual susceptibility and sanitary factors may influence the occurrence of natural infections by gastrointestinal protozoans, although the age did not have influence. This study reports, for the first time, the occurrence of Cryptosporidium sp., Giardia sp. and E. leuckarti in equines of the State of Rio de Janeiro.     

Prevalence and molecular characterization of bovine Cryptosporidium in Qazvin province, Iran

The aim of this study was to determine the prevalence, variability with host age, and the genotypes of species of Cryptosporidium in cattle from 15 dairy farms in Qazvin province, Iran. Fecal samples, collected from 272 cattle during May 2006 to December 2007, were characterized microscopically. Oocysts from 51 positive samples were analyzed using PCR assay of 18S SSU rRNA, restriction fragment length polymorphism (RFLP) and sequencing. We identified 72.6% of the positive samples as Cryptosporidium parvum, 17.7% as Cryptosporidium andersoni, 7.8% as Cryptosporidium bovis and 1.9% as a novel genotype of C. parvum possessing a single mutation on MboII restriction. An infection rate of 19.5% of C. parvum among 174 pre-weaned calves was significantly higher than the 3.1% among 98 post-weaned calves (P < 0.0006). This is the first report of C. bovis and the new subgenotype of C. parvum in Iranian cattle.     

Neem-tree (Azadirachta indica Juss.) extract as a feed additive against the American dog tick (Dermacentor variabilis) in sheep (Ovis aries)

Acaricides can be conveyed to ticks via the blood of their hosts. As fruit and kernel extracts from the Meliaceae family, and, in particular the tetranortriterpenoid azadirachtin (AZA) inhibits tick egg production and embryogenesis in the Ixodidae ticks, we investigated the effects of Neem Azal^®, an extract containing 43% AZA, given as a feed additive to lambs artificially infested with engorging adult Dermacentor vairiabilis ticks. After tick attachment, the lambs were allotted to three dietary treatments: AZA0 (control, n = 10), AZA0.3 (n = 5), and AZA0.6 (n = 5), with feed containing 0%, 0.3%, and 0.6% AZA on DM basis, respectively. In half of the AZA0 lambs, ticks were sprayed on day 4 after attachment with an ethanol:water:soap emulsion containing 0.6% AZA (AZA0S). In spite of its very pungent odor, the neem extract was well accepted by all but one lamb. No differences were found between treatment groups in liver enzymes in blood, and there was no indication of toxicity. The plasma AZA concentrations after 7 and 14 days of feeding AZA were (4.81 and 4.35 μg/mL) for the AZA0.6 and (3.32 and 1.88 μg/mL) for the AZA0.3 treatments, respectively (P < 0.0001). Treatments were not lethal to ticks, but tick weights at detachment were 0.64, 0.56, 0.48, and 0.37 g for ticks from the AZA0, AZA0.3, AZA0S, and AZA0.6 treatments (P < 0.04), respectively, suggesting that blood AZA impaired blood-feeding. The highest mortality rate after detachment was for AZA0.6 (P < 0.09). As AZA affects embryo development and ticks at the molting stages, we expect that following treatments of hosts for longer periods, one-host ticks will be more affected than the three-host tick D. variabilis.     

Epidemiology of Campylobacter jejuni in raccoons (Procyon lotor) on swine farms and in conservation areas in southern Ontario

Campylobacter is a leading cause of foodborne illness in humans worldwide. Sources of infection are often difficult to identify, and are, generally, poorly understood. Recent work suggests that wildlife may represent a source of Campylobacter for human infections. Using a repeated cross‐sectional study design, raccoons were trapped on five swine farms and five conservation areas in southern Ontario from 2011 to 2013. Our objectives were to: (a) assess the impact of seasonal, climatic, location, annual and raccoon demographic factors on the occurrence of Campylobacter jejuni in these animals; and (b) identify clusters of C. jejuni in space, time and space‐time using spatial scan statistics. Multi‐level multivariable logistic regression was used to examine the odds of isolating C. jejuni, with site and animal modelled as random intercepts. The following independent variables were examined: raccoon age and sex, year, location type, season, temperature and rainfall. A total of 1,096 samples were obtained from 627 raccoons; 46.3% were positive for C. jejuni. The following interactions and their main effects were significant (p < .05) and retained in the final model: season × temperature, year × rainfall, year × temperature. Based on the results from our multivariable model and spatial scan statistics, climatic variables (i.e. rainfall, temperature and season) were associated with the carriage of C. jejuni by raccoons, but the effects were not consistent, and varied by location and year. Although raccoons may pose a zoonotic risk due to their carriage of Campylobacter, further work is required to characterize the transmission and movement of this microorganism within the ecosystem.     

Comparison of the susceptibility of brown trout (Salmo trutta) and four rainbow trout (Oncorhynchus mykiss) strains to the myxozoan Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD)

Differences in susceptibility to the myxozoan parasite Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD), between four strains of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) were evaluated. Fish were exposed to water enzootic for the parasite in the field for 5 days and were subsequently transferred to the laboratory. Relative parasite load was determined after 2, 3 and 4 weeks post-exposure (wpe) by quantitative real-time PCR (qPCR) of kidney samples and number of parasite stages was determined in immunohistochemical stained sections of kidney, liver and spleen tissues. According to qPCR results, the highest amount of parasite DNA per equal amount of host tissue at all time points was measured in brown trout. Two of the rainbow trout strains showed lower relative parasite load than all other groups at the beginning of the experiment, but the parasite multiplied faster in these strains resulting in an equal level of relative parasite load for all rainbow trout strains at 4 wpe. A weak negative correlation of fish size and parasite load was detected. Only in samples of a few fish, single stages of T. bryosalmonae were found in sections stained by immunohistochemistry impeding quantitative evaluation of parasite numbers by this method. The results indicate a differential resistance to T. bryosalmonae between the rainbow trout strains investigated and between rainbow trout and brown trout.     

Antibody-ELISA for Trypanosoma evansi: Application in a serological survey of dairy cattle, Thailand, and validation of a locally produced antigen

Trypanosoma evansi is generally considered a mild pathogen in bovines. However, in Asia, acute and chronic signs have been observed in cattle, with high levels of parasitaemia, abortion and death. Investigations in Asian cattle are needed to better understand this epidemiological situation. To generate comparable data at a regional level, development and standardization of an antibody-enzyme linked immunosorbent assay for T. evansi (ELISA/T. evansi) was initiated and applied in an epidemiological survey carried out in dairy cattle in Thailand. A batch of 1979 samples was collected from dairy farms located throughout the country's four regions. Soluble T. evansi antigens initially produced in France were also produced in Thailand for comparison and technology transfer. Screening of 500 samples allowed us to identify reference samples and to determine the cut-off value of the ELISA. Seropositive animals – some of them confirmed by PCR – were found in the four regions, in 12 out of 13 provinces, in 22 out of 31 districts, in 56 farms out of 222 (25%, 95%CI ± 6%) and in 163 animals out of 1979 (8.2, 95%CI ± 1.2%). Estimated seroprevalence in 35 farms ranged between 1% and 30%, and in 21 farms it was >30%. Approximately 25% of survey cattle were exposed to the infection, in various situations. A sub-sample of 160 sera was tested on both antigens. Wilcoxon's (Z = 1.24; p = 0.22) and McNemars's tests (CHI2 = 3.55; p = 0.09) did not show any significant differences, showing that the locally produced antigen is suitable for further evaluation in the surrounding countries. Use of this standardized serological method will broaden knowledge of the prevalence and impact of the disease at the regional level in South-East Asia. Further validation of this ELISA will be necessary in other host species such as buffalo, horse and pig.     

Hemorrhagic Gastritis Associated with Renal Failure, Hemoglobinuria, and Isolation of Clostridium perfringens in a Horse

A 3-year-old Quarter Horse mare was presented for acute colic with bright red-black foul-smelling gastric reflux containing long rod-shaped bacteria consistent with Clostridium sp. and red-black urine. The serum creatinine concentration was 5.5 mg/dL (N = 0.9–1.7), and blood urea nitrogen was 41 mg/dL (N = 9–20). At necropsy, the stomach wall was diffusely thickened, hemorrhagic, and edematous. Histopathologically, hemorrhagic necrosis was evident, with numerous colonies of spore-forming rods within the submucosa. Clostridium perfringens was cultured from the stomach contents. Polymerase chain reaction (PCR) genotyping was consistent with type A C. perfringens. Bilaterally, the kidneys were grossly enlarged, diffusely dark red-brown, and congested. The renal tubular epithelium was diffusely, acutely necrotic, with interstitial hemorrhage and massive accumulation of intratubular granular and proteinaceous casts. A diagnosis of massive hemolysis with hemoglobinuria and renal failure due to C. perfringens, type A infection was made. Alpha-toxin–induced intravascular hemolysis occurs rarely in humans and sheep. To our knowledge, this has not been described in horses with clostridial enterocolitis nor in equine clostridial gastritis.     

Prevalence and intensity of Otodectes cynotis in kittens from Thessaloniki area, Greece

From May 2007 to May 2008 we have examined by otoscopy a total number of 214 cats, aged between 0 and 6 months, brought in for their first veterinary examination to a private veterinary clinic. All cats were of urban origin. In all positive cats we performed a washing of the ear using warm paraffin oil in order to determine intensity of infection. Statistical analysis was performed using the Chi-square test. A total number of 30 cats were found to be infected with Otodectes cynotis (prevalence 14.02%). Prevalence of infection was significantly (p < 0.05) higher in cats aged between 3 and 6 months (17.58%) than in cats aged below 3 months (11.38). Intensity of infection ranged between 7 and 85 (mean intensity 35.60) mites per infected cat. The same age group of cats between 3 and 6 months had significantly (p < 0.05) higher mean intensity (47.19) compared to cats aged under 3 months (22.36). No statistical significance was found between males and females for neither prevalence nor intensity. Differences and similarities with other studies are discussed.     

Mortality and recovery of runt white sturgeon (Acipenser transmontanus) in a commercial farm in California, USA

We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m × 2 m rectangular tanks and graded periodically during a follow-up of 46–102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46–89 day period is substantial (16–58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg.     

Prevalence of Calodium hepaticum (Syn. Capillaria hepatica) in house mice (Mus musculus) in the Azores archipelago

Calodium hepaticum (Syn. Capillaria hepatica) is a zoonotic liver nematode of mammals distributed worldwide. Rodents are believed to be the main reservoirs of this nematode. In this paper, prevalence of the parasite was analyzed in liver histological sections from 51 house mice (Mus musculus) caught in human-inhabited houses, from two localities (Furnas and Rabo de Peixe) on São Miguel island from the Azores archipelago (Portugal). Mean prevalence of infection was 19.6%, with 33.3% prevalence in Furnas and 4.1% in Rabo de Peixe (P = 0.07). No significant differences were found between the prevalence of infection and the age, body weight and the sex of mice. Hepatic lesions found were either acute and/or chronic stage and consisted of moderate to severe multifocal pyogranulomatous hepatitis with encapsulated eggs with typical bipolar plugs and moderate to severe necrotizing hepatitis consistent with larva tracks. Periportal inflammatory infiltration, hepatocyte regeneration and bile duct hyperplasia were also noted. In most cases, hepatic lesions occupied more than 50% of the liver, but despite severe lesions, in some mice, no signs of hepatic failure were noticed. The high rate of infection found in the present study suggests that house mice are an important reservoir for this parasite in the Azores and could have a role in human transmission.     

Effect of varying ruminally degradable to ruminally undegradable protein ratio on nutrient intake, digestibility and N metabolism in Nili Ravi buffalo calves (Bubalus bubalis)

Four Nili-Ravi buffalo calves (100 ± 4 kg) were used in 4 × 4 Latin Square Design to evaluate the influence of varying ruminally degradable protein (RDP) to ruminally undegradable protein (RUP) ratio on dry matter intake (DMI), digestibility and nitrogen (N) metabolism. Four experimental diets A, B, C and D were formulated to contain RDP:RUP of 70:30, 65:35, 60:40 and 55:45, respectively. The calves were fed ad libitum. Dry matter intake by calves fed C diet was higher (P < 0.05) than those fed D diet and lower (P < 0.05) than calves fed A diet, however, it was similar to those fed B diet. There was a linear decrease (P < 0.01) in DMI with decreasing the RDP to RUP ratio. Similar trend was noticed in crude protein (CP) intake. Neutral detergent fiber (NDF) intake was significantly different across all treatment. The decrease in CP and NDF intake was due to decreasing trend of DMI. Dry matter (DM) digestibility in calves fed A and B diets was higher (P < 0.05) than those fed C and D diets. A linear decrease (P < 0.01) in DM digestibility was observed with decreasing the RDP to RUP ratio. Crude protein digestibility remained unaltered across all treatments. Neutral detergent fiber digestibility was higher in calves fed A and B diets than those fed C and D diets. Higher NDF digestibility in calves fed A and B diets was due to higher level of dietary RDP that might resulted in higher ruminal ammonia concentration which stimulate activity of cellulytic bacteria and ultimately increased NDF digestibility. The N retention (g/d) was similar among the calves fed B, C and D diets, however, it was higher (P < 0.05) than those fed A diet. Decreasing the RDP to RUP ratio resulted in linear increase (P < 0.01) in N retention. The N retention, as percent of N intake was significantly different across all treatments. Decreasing RDP to RUP ratio resulted in linear increase (P < 0.01) in N retention, as percent of N intake. A similar trend was noticed in N retention, as percentage of N digestion. Blood urea nitrogen (BUN) concentration in calves fed B diet was higher (P < 0.05) than those fed D diet and was lower (P < 0.05) than those fed A diet, however, it was not different from calves fed C diet. Decreasing dietary RDP to RUP ratio resulted in linear decrease (P < 0.05) in BUN concentrations. The decrease in BUN concentration was because of decreasing level of dietary RDP. The N retention can be increased by decreasing RDP to RUP ratio in the diet of growing buffalo calves and diet containing RDP to RUP ratio 55:45 is considered optimum regarding N retention in buffalo calves.     

Rearing unit-level factors associated with bacterial gill disease treatment in two Ontario, Canada government salmonid hatcheries

Early-rearing salmonids in Ontario Ministry of Natural Resources (OMNR) fish hatcheries have been consistently affected by bacterial gill disease (BGD) (causative agent: Flavobacterium branchiophilum) for many years. Separate retrospective epidemiological investigations of BGD treatments at two OMNR fish hatcheries (Hatcheries A and B) for the 1999 production year were conducted using on-site hatchery records. Both investigations were carried out at the rearing unit-level, with early-rearing (<9 months of age) “tank-lot” as the unit of analysis to identify unique fish populations over time. Multivariable repeated measures logistic regression models were created for both hatchery datasets, controlling for lot-level and species effects. For Hatchery A, the species brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) were significantly associated with BGD treatment, as well as lower water exchange rate, and higher feeding and mortality percentages during the 2 weeks previous to BGD treatment. At Hatchery B, the species brook trout (S. fontinalis) and splake (Salvelinus namaycush × S. fontinalis) were significantly associated with BGD treatment, as well as lower individual fish weights and treatment for BGD during the previous week. These results emphasize the importance of water quality, feeding rate, fish size and prior mortality on the development of BGD. Significant hatchery and species effects were evident, and future observational research on BGD must account for these factors in their design and analysis.     

Personal and household factors involved in recent Rickettsia exposure in a rural population from Yucatán,Mexico

The aim of the study was to describe the epidemiological factors associated with the risks of recent Rickettsia exposure in inhabitants of a rural population from Yucatán, Mexico. The study included 130 inhabitants from Maxcanú, Yucatán. Blood samples were collected to detect IgM and IgG antibodies against Rickettsia typhi and Rickettsia rickettsii by an indirect immunofluorescence antibody test. Additionally, nested polymerase chain reaction was performed to amplify fragments of the 17kDa and sca5 genes. Previously, an epidemiological questionnaire was applied focused on collecting information on personal and housing exposure variables related to the recent infection with Rickettsia to determine epidemiological associations. Results that exhibited a p‐value < .25 were included in a generalized multinomial logistic linear model to determine the variables involved with the risk of contact or Rickettsia infection. In all, 76% (99/130) of the participants presented with immunoglobulin titres against the Rickettsia species evaluated, while rickettsial DNA was detected in 35.4% (46/130) of the participants. The association analysis with the personal exposure variables showed that the productive age group (OR = 0.32; 95% CI = 0.10–1.03) and the elders group (OR = 0.12; 95% CI = 0.01–0.83) were protective factors for recent infection with R. typhi, taking as reference the school group. The presence of a family orchard in the home (OR = 7.56; 95% CI = 1.62–35.29) was a risk factor for recent infection with R. rickettsii. Presumably, the presence of ectoparasites (OR = 2.71; 95% CI = 0.90–8.09) at home was a risk factor for recent infection with both Rickettsia species. Recent infection was demonstrated in inhabitants from Maxcanú, Yucatán. A high seropositive frequency was obtained. The results highlight the importance of the family garden and the presence of ectoparasites in the home as risk factors associated with recent infection with Rickettsia in inhabitants from Maxcanú.     

Effects of Teladorsagia (Ostertagia) circumcincta infection on lambs selected for high fleece weight

The physiological processes leading to the expression of the resilient phenotype, which allow animals to maintain a relatively higher production level during infection, have been investigated in lambs from a closed flock selected for 40 generations for high fleece weight (HFW), but with higher FEC and worm burdens than their unselected control (C) flock run in parallel. After recovery from surgery to implant abomasal cannulae, eight parasite-naïve lambs from each flock were infected intraruminally at 4.5 months-of-age with 50,000 Teladorsagia circumcincta L3. Blood, abomasal fluid and faecal samples were collected daily for measurement of serum gastrin and pepsinogen concentrations, blood eosinophils, abomasal pH and FEC. Four lambs from each flock were euthanased on Day 8 post-infection and the other four on Day 28 post-infection. At necropsy, abomasal contents and tissues were collected for worm counts, abomasal lymph nodes and fundic tissue for cytokine gene expression and fundic tissue for histopathology. Expression of resilience appeared to be age-dependent as there were no significant differences in either FEC or worm burden between lambs from the two flocks, unlike older HFW lambs in a previous study. Abomasal secretion did not differ between flocks. Histopathological changes were typical of parasitism: inflammatory cells, mainly eosinophils and lymphocytes, were numerous in nodular areas and there were fewer TGF-α positive parietal cells, many of which were vacuolated. By Day 28 p.i., globule leucocytes were present. Mucosal thickness was significantly greater on Day 8 than Day 28 p.i. (p = 0.000) and in C than HFW lambs. There were fewer parietal cells on Day 28 than on Day 8 p.i. (p = 0.003) for pooled data. Circulating eosinophil counts increased moderately in both groups, significantly less in the HFW lambs. Fewer tissue and blood eosinophils in the HFW than C group on Day 8 p.i. were consistent with cytokine gene expression patterns, particularly lower IL-5 levels. Worm count decreased by 90% by Day 28 p.i., along with declining tissue eosinophil counts and IL-13 gene expression and increasing IL-10 and IL-4 gene expression. Food intake was depressed less in the HFW lambs, suggesting that maintenance of appetite could be an important aspect of the physiological basis for resilience. Although the resilient phenotype was not apparent at the younger age, lesser effects on food intake, differences in ALN cytokine profiles and lower blood and tissue eosinophil numbers in the HFW lambs may lead to the expression of resilience when older.     

Beyond abundance: How microenvironmental features and weather influence Bartonella tribocorum infection in wild Norway rats (Rattus norvegicus)

Norway rats (Rattus norvegicus) inhabit cities worldwide and carry a number of zoonotic pathogens. Although many studies have investigated rat‐level risk factors, there is limited research on the effects of weather and environment on zoonotic pathogen transmission ecology in rats. The objective of this study was to use a disease ecology approach to understand how abiotic (weather and urban microenvironmental features) and biotic (relative rat population abundance) factors affect Bartonella tribocorum prevalence in urban Norway rats from Vancouver, British Columbia, Canada. This potentially zoonotic pathogen is primarily transmitted by fleas and is common among rodents, including rats, around the world. During a systematic rat trap and removal study, city blocks were evaluated for 48 environmental variables related to waste, land/alley use and property condition, and rat abundance. We constructed 32 weather (temperature and precipitation) variables with time lags prior to the date we captured each rat. We fitted multivariable logistic regression models with rat pathogen status as the outcome. The odds of a rat testing positive for B. tribocorum were significantly lower for rats in city blocks with one or more low‐rise apartment buildings compared to blocks with none (OR = 0.20; 95% CI: 0.04–0.80; p = .02). The reason for this association may be related to unmeasured factors that influence pathogen transmission and maintenance, as well as flea vector survival. Bartonella tribocorum infection in rats was positively associated with high minimum temperatures for several time periods prior to rat capture. This finding suggests that a baseline minimum temperature may be necessary for flea vector survival and B. tribocorum transmission among rats. There was no significant association with rat abundance, suggesting a lack of density‐dependent pathogen transmission. This study is an important first step to understanding how environment and weather impacts rat infections including zoonotic pathogen ecology in urban ecosystems.     

Acaricidal effects of the essential oil of Origanum minutiflorum (Lamiaceae) against Rhipicephalus turanicus (Acari: Ixodidae)

The acaricidal effects of the volatile essential oil Origanum minutiflorum O. Schwarz & P.H. Davis (Lamiaceae) against adult Rhipicephalus turanicus was evaluated at a variety of concentrations and exposure times. Generally tick mortality increased with concentration and exposure. Ticks exposed to vapors from cotton wicks containing at least 10 μl/L resulted in complete (100%) mortality at 120 min. The major constituent of essential oil obtained from the plant material of O. minutiflorum was carvacrol.