The effect of constant low temperatures on the survival of Bulinus africanus (Krauss), Bulinus globosus (Morelet) and Biomphalaria pfeifferi (Krauss)

The tolerance to low temperature of the freshwater snail species Bulinus africanus, Bulinus globosus and Biomphalaria pfeifferi was experimentally investigated. Snails were exposed to temperatures ranging from 0 °C to 8 °C and their survival was noted daily. The results showed that the survival of the cohorts of all three species decreased as the temperature was lowered in the range investigated. Evidence is presented which demonstrates that B. africanus can withstand cold conditions better than B. globosus, and that a globosus is better equipped than a pfeifferi in withstanding low water temperatures.     

An enclosure study to evaluate the effect of Sargochromis codringtoni on snail populations in an irrigation canal

The cichlid fish, Sargochromis codringtoni has been suggested as an alternative to the use of molluscicides for controlling schistosome intermediate host snails. To determine the effect of the fish on Bulinus globosus and Biomphalaria pfeifferi populations in irrigation canals, an enclosure experiment was carried out. The presence of fish was found to significantly reduce the numbers of both B. globosus and B. pfeifferi.     

Effect of temperature on growth,survival and reproduction of Bulinus nyassanus (Smith, 1877) (Mollusca: Gastropoda) from Lake Malawi

Bulinus nyassanus, endemic to Lake Malawi, is an intermediate host for Schistosoma haematobium and plays an important role in transmission of this parasite along some shorelines on the Nankumba Peninsula in the southern part of the lake. Density of B. nyassanus in shallow water is usually low from January to April and a major population increase takes place during May to August when water temperatures are relatively low (about 22°C) and supposedly suboptimal for B. nyassanus. This study was designed to compare performance (growth, reproduction, survival, and hatchability of egg-masses) of B. nyassanus at four constant temperatures (22, 25, 28 and 31°C). Survival and reproduction were optimal at 25°C while growth and egg development were faster at the higher temperatures. Findings are discussed in view of the population dynamics of B. nyassanus at Cape Maclear.     

Has Sarcocystis neurona Dubey et al., 1991 (Sporozoa: Apicomplexa: Sarcocystidae) cospeciated with its intermediate hosts?

The question of how Sarcocystis neurona is able to overcome species barrier and adapt to new hosts is central to the understanding of both the evolutionary origin of S. neurona and the prediction of its field host range. Therefore, it is worth reviewing current knowledge on S. neurona host specificity. The available host range data for S. neurona are discussed in relation to a subject of evolutionary importance—specialist or generalist and its implications to understand the strategies of host adaptation. Current evidences demonstrate that a wide range of hosts exists for S. neurona. This parasite tends to be highly specific for its definitive host but much less so for its intermediate host (I.H.). The unique specificity of S. neurona for its definitive host may be mediated by a probable long coevolutionary relationship of the parasite and carnivores in a restricted ecological niche ‘New World’. This might be taken as evidence that carnivores are the ‘original’ host group for S. neurona. Rather, the capacity of S. neurona to exploit an unusually large number of I.H. species probably indicates that S. neurona maintains non-specificity to its I.H. as an adaptive response to insure the survival of the parasite in areas in which the ‘preferred’ host is not available. This review concludes with the view that adaptation of S. neurona to a new host is a complex interplay that involves a large number of determinants.     

Thermoregulation of the subterranean rodent genus Bathyergus (Bathyergidae)

The thermoregulation of the largest subterranean rodent, genus Bathyergus, comprising two species, B. suillus and B. janetta, occurring in mesic and semiarid habitats respectively, was investigated and compared with that of other subterranean rodents. Both species display low resting metabolic rates and low body temperatures characteristic of subterranean rodents. The lower metabolism and smaller body size of B. janetta, may be an ‘energy-saving’ adaptation to its semi-arid habitat.     

Potential value of tedera (B. bituminosa) as high protein resource for poultry feed

Bituminaria bituminosa (C.H. Stirt.) is a drought tolerant legume that grows spontaneously in subtropical areas: Canary Islands (Spain) and in North African and Mediterranean regions, traditionally used as forage for ruminants. The aim of this research was to investigate the potential of B. bituminosa as a high protein resource for poultry feed by means of feed intake, growth, feed conversion rate (FCR), protein efficiency ratio (PER), and the influence of B. bituminosa feed form (fresh green and dried) on the preference by chicks. B. bituminosa showed higher crude protein content (CP), neutral detergent fiber (NDF), and gross energy than commercial feed. Average daily feed intake (ADFI) for the commercial feed group (control group) was higher than ADFI of the B. bituminosa group (experimental group). However, both groups had no significant differences in total crude protein intake, total NDF intake, average daily gain (ADG), FCR, and PER. The poultry’s preference for fresh green B. bituminosa was higher than for dry B. bituminosa. Our results suggest that B. bituminosa (tedera) could be an alternative feedstuff in tropical countries or where protein sources are scarce and costly.

     

Sialylation of Helicobacter bizzozeronii lipopolysaccharides modulates Toll-like receptor (TLR) 2 mediated response

Sialic acid in lipopolysaccharides (LPS) of mucosal pathogens is known to be an important virulence factor. Few strains of Helicobacter pylori express sialyl-Lewis-X and we have reported that human and canine Helicobacter bizzozeronii strains express sialyl-lactoseamine in their LPS. However, the role of sialyation of Helicobacter LPS in the interaction with the host cells is still unknown. In this study H. bizzozeronii LPS is shown to activate the TLR2 in a dose and strain dependent manner in the in vitro HEK-293 cells model expressing TLR2, but not the cells expressing TLR4. These results indicate that TLR2 is the specific receptor for H. bizzozzeronii LPS, as previously described for H. pylori. To further explore the role of sialylation of H. bizzozeronii LPS on TLR2 response, H. bizzozeronii Δhbs2 mutant strains deficient in sialyltransferase activity were constructed by homologous recombination. LPS from H. bizzozeronii Δhbs2 strains enhanced the NF-ĸB induction via TLR2 compared to the respective wild types, leading to the conclusion that the sialylation of H. bizzozeronii LPS in wild-type strains may modulate host immune response.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-014-0133-4) contains supplementary material, which is available to authorized users.     

Egg trait variation in a large hawk‐cuckoo (Hierococcyx sparverioides) host population of Chinese babax (Babax lanceolatus)

Mutual interaction between brood parasites and their hosts is a well‐known model system for studying host–parasite coevolution. Both parties have acted reciprocally, resembling an evolutionary arms race, in which adaptations and counter‐adaptations have evolved as a result of host–parasite dynamics, such as the classical cuckoo–host system. Discrimination among parasite and cuckoo eggs and rejection of foreign eggs is regarded as an important anti‐parasitism strategy. The Chinese babax (Babax lanceolatus) is a large hawk‐cuckoo (Hierococcyx sparverioides) host distributed in southwest China. A previous study shows that the babax is an intermediate egg rejector, and most cuckoo eggs are accepted by the Chinese babax, although a small proportion of hosts reject cuckoo eggs. Interestingly, the large hawk‐cuckoo lays non‐mimetic eggs in contrast to the uniform blue eggs of babaxes. Because egg coloration is a critical cue used by host species in favor of the recognition of parasitic eggs by hosts, we used a spectrometer to quantify egg color variation to understand the differentiation in discrimination ability between the egg rejectors and acceptors. We found that the chroma of intra‐clutch variation of babax eggs was more consistent in egg rejectors than in acceptors. However, no statistical significance was found in inter‐clutch variation between these two types of hosts. Our results suggest that hosts lay eggs with a low level of intra‐clutch variation without the necessity of a high level of inter‐clutch variation simultaneously as predicted by the egg signature hypothesis. This study may further indicate that selection pressures from evolutionarily recent parasites can drive individual‐based differences in an anti‐parasitism strategy.     

Longevity of Bolbophorus damnificus Infections in Channel Catfish

Abstract

The digenean Bolbophorus damnificus infects commercial channel catfish Ictalurus punctatus, causing mortality, lower feed consumption, and reduced growth in surviving fish. The purpose of this study was to determine the length of time for which B. damnificus prodiplostomulum metacercariae (juvenile trematode stage that infects fish) would remain viable (parasite appearing to be intact or exhibiting movement) in channel catfish. Fish (n = 210) were infected with molecularly confirmed B. damnificus cercariae harvested from naturally infected marsh rams-horn snails Planorbella trivolvis. During the first sampling (at 20 d postinfection), 8.3 ± 3.6 metacercariae/fish (mean ± SD) were found in the host muscle and visceral organs. The channel catfish were then acclimated to a water temperature of either 18°C or 28°C. After 11 months, 6.8 ± 3.5 and 5.9 ± 3.0 metacercariae/fish were found in groups held at 18°C and 28°C, respectively. The mean number of parasites per fish did not significantly differ between fish held at the two temperatures and did not significantly decline over time at either temperature. Fish examined from 13 to 30 months postinfection all contained viable metacercariae that were morphologically and molecularly identified as B. damnificus. At 18 months, 12 metacercariae (of which 11 were intact and 10 displayed movement) were found in the one fish sampled; at 30 months, the last fish sampled contained three intact metacercariae (one displayed slight movement). Our results indicate that B. damnificus metacercariae can remain viable in channel catfish for at least an 18–30-month production cycle during which they have the potential to affect fish growth; in addition, infected fish may serve as intermediate hosts for these metacercariae for at least 2.5 years postinfection.

Received July 14, 2010; accepted March 6, 2011     

Comparative Susceptibility of Channel Catfish,Blue Catfish,and their Hybrid Cross to Experimental Challenge with Bolbophorus damnificus (Digenea: Bolbophoridae) Cercariae

Abstract

The digenetic trematode Bolbophorus damnificus has been implicated in significant losses in catfish aquaculture since the late 1990s. The complex life cycle sequentially involves the American white pelican Pelecanus erythrorhynchos, the marsh rams horn snail Planorbella trivolvis, and Channel Catfish Ictalurus punctatus. Research supports anecdotal reports from the industry, suggesting that the hybrid of Channel Catfish×Blue Catfish I. furcatus is less susceptible to disease agents that have been historically prohibitive to Channel Catfish production, namely the gram-negative bacteria Edwardsiella ictaluri and Flavobacterium columnare, as well as the myxozoan parasite Henneguya ictaluri. This current research compared the susceptibility of Channel Catfish, Blue Catfish, and their hybrid cross to an experimental challenge by B. damnificus. Fish were exposed to 0, 100, 200, and 400 B. damnificus cercariae per fish, and the numbers of metacercariae per fish were determined 14 d postchallenge. Metacercariae were recovered from all challenged fish. There were no significant differences among fish groups challenged with the same dose, suggesting Channel and Blue Catfish and their hybrid are comparably susceptible to B. damnificus infection. As such, it is recommended that producers raising hybrid catfish remain diligent in controlling populations of the snail intermediate host to prevent production losses attributed to B. damnificus, especially when loafing pelicans have been observed at the aquaculture operation.

Received October 22, 2013; accepted January 5, 2014     

Sarcocystid organisms found in bile from a dog with acute hepatitis: a case report and review of intestinal and hepatobiliary Sarcocystidae infections in dogs and cats

Sarcocystidae is a family of coccidian protozoa from the phylum Apicomplexa that includes Toxoplasma, Neospora, Sarcocystis, Hammondia, and Besnoitia spp. All species undergo a 2‐host sexual and asexual cycle. In the definitive host, replication is enteroepithelial, and infection is typically asymptomatic or less commonly causes mild diarrhea. Clinical disease is most frequently observed in the intermediate host, often as an aberrant infection, and is mostly associated with neurologic, muscular, or hepatic inflammation. Here, we review the literature regarding intestinal Sarcocystidae infections in dogs and cats, with emphasis on the life cycle stages and the available diagnostic assays and their limitations. We also report the diagnostic findings for an 11‐year‐old dog with acute neutrophilic hepatitis, biliary protozoa, and negative biliary culture. Although Toxoplasma and Neospora IgG titers were both high, PCR for these 2 organisms was negative for bile. The organisms were identified by 18S rDNA PCR as most consistent with Hammondia, either H heydorni or H triffittae. This is the first report of presumed Hammondia organisms being found in canine bile.     

The devil is in the details—Host disease and co‐infections are associated with zoonotic pathogen carriage in Norway rats (Rattus norvegicus)

Traditionally, zoonotic pathogen ecology studies in wildlife have focused on the interplay among hosts, their demographic characteristics and their pathogens. But pathogen ecology is also influenced by factors that traverse the hierarchical scale of biological organization, ranging from within‐host factors at the molecular, cellular and organ levels, all the way to the host population within a larger environment. The influence of host disease and co‐infections on zoonotic pathogen carriage in hosts is important because these factors may be key to a more holistic understanding of pathogen ecology in wildlife hosts, which are a major source of emerging infectious diseases in humans. Using wild Norway rats (Rattus norvegicus) as a model species, the purpose of this study was to investigate how host disease and co‐infections impact the carriage of zoonotic pathogens. Following a systematic trap and removal study, we tested the rats for the presence of two potentially zoonotic bacterial pathogens (Bartonella tribocorum and Leptospira interrogans) and assessed them for host disease not attributable to these bacteria (i.e., nematode parasites, and macroscopic and microscopic lesions). We fitted multilevel multivariable logistic regression models with pathogen status as the outcome, lesions and parasites as predictor variables and city block as a random effect. Rats had significantly increased odds of being infected with B. tribocorum if they had a concurrent nematode infection in one or more organ systems. Rats with bite wounds, any macroscopic lesion, cardiomyopathy or tracheitis had significantly increased odds of being infected with L. interrogans. These results suggest that host disease may have an important role in the ecology and epidemiology of rat‐associated zoonotic pathogens. Our multiscale approach to assessing complex intrahost factors in relation to zoonotic pathogen carriage may be applicable to future studies in rats and other wildlife hosts.     

Occurrence,Virulence Genes and Antibiotic Resistance of Enteropathogenic Escherichia coli (EPEC) from Twelve Bovine Farms in the North‐East of Ireland

Cattle faecal samples (n = 480) were collected from a cluster of 12 farms, and PCR screened for the presence of the intimin gene (eae). Positive samples were cultured, and colonies were examined for the presence of eae and verocytotoxin (vtx) genes. Colonies which were positive for the intimin gene and negative for the verocytotoxin genes were further screened using PCR for a range of virulence factors including bfpA, espA, espB, tir ehxA, toxB, etpD, katP, saa, iha, lpfA_{O157/OI‐141} and lpfA_{O157/OI‐154.} Of the 480 faecal samples, 5.8% (28/480) were PCR positive, and one isolate was obtained from each. All 28 isolates obtained were bfpA negative and therefore atypical EPEC (aEPEC). The serotypes detected included O2:H27, O8:H36, O15:H2, O49:H+, O84:H28, O105:H7 and O132:H34 but half of the isolates could not be serogrouped using currently available antisera. Twenty‐two (79%) of the isolates carried the tir gene but only 25% were espB positive, and all other virulence genes tested for were scarce or absent. Several isolates showed intermediate resistance to ciprofloxacin, kanamycin, nalidixic acid, minocycline and tetracycline; full resistance to nalidixic acid or tetracycline with one isolate (O?:H8) displaying resistance to aminoglycosides (kanamycin and streptomycin), quinolones (nalidixic acid) and sulphonamides. This study provides further evidence that cattle are a potential source of aEPEC and add to the very limited data currently available on virulence genes and antibiotic resistance in this pathogenic E. coli group in animals.     

A New Eye Disease in Pen-Reared Chinook Salmon Caused by Metacestodes of Gilquinia squali (Trypanorhyncha)

Abstract

Eye infections by metacestodes of Gilquinia squali (Cestoda: Trypanorhyncha) were associated with mortality in chinook salmon Oncorhynchus tshawytscha reared in net-pens in seawater at two separate locations in British Columbia. Mortality associated with the disease was about 10% at one site and undetermined at the second site. The metacestode was found in the vitreous humor of moribund fish with eye lesions, whereas healthy fish from the same pen exhibited neither eye lesions nor the infection. The lesions were characterized by retinal folding and apparent retinal duplication, and cataractous changes; in severe cases, the cornea ruptured, and the lens was extruded. The spiny dogfish Squalus acanthias i s the definitive host for the cestode. Spiny dogfish were prevalent in and around the affected net-pen sites, thus providing coracidia to infect the first intermediate host, which is most likely a crustacean. Although the metacestode is common in the eyes of European whiting Merlangius merlangus in the northeast Atlantic region, this is the first report of the infection in a salmonid.     

Characterization and partial purification of a bacteriocin‐like substance produced by thermophilic Bacillus licheniformis H1 isolated from cow manure compost

The production and partial characterization of bacteriocin‐like substances (BLSs) produced by bacteria isolated from cow manure compost were investigated. Eight BLS producers, which exhibited inhibitory activity against pathogenic bacteria, were isolated from cow manure compost at different stages of the composting process. The pile temperature ranged from 9.1°C to 73.2°C. The BLSs showed thermostability, but the BLS producers were not thermostable except for the H1 producer. Thermophilic Bacillus licheniformis H1 was further characterized. The culture supernatant of B. licheniformis H1 exhibited antagonistic activity against various species of Gram‐positive bacteria such as Listeria monocytogenes ATCC19111 but not against Gram‐negative bacteria except Pseudomonas fluorescens ATCC11251. Inactivation of bacteriocin‐like activity by α‐chymotrypsin, trypsin, and papain was highly significant (P < 0.001). The BLS was found to be stable under a pH range from 3 to 9 and at temperatures up to 75°C for 60 min, but it lost activity after being autoclaved at 121°C for 15 min. The optimum production of BLS by B. licheniformis H1 was obtained at a temperature of 55°C. Sodium dodecyl sulfate – polyacrylamide electrophoresis analysis of concentrated partially purified supernatants collected after resting the bacterial cells at 55°C revealed a bacteriocin‐like protein with a molecular mass of approximately 3.5 kDa. This study is the first report of a BLS from thermophilic B. licheniformis with an animal compost origin.     

First account of the metazoan parasite fauna of oilfish Ruvettus pretiosus Cocco, 1829 (Perciformes: Gempylidae) in South African waters

Parasites are an important but neglected component of ecosystems that can be used as indicators of host biology and ecology. In the present study, the metazoan parasite assemblage of Ruvettus pretiosus, an understudied but widely distributed predatory gempylid, caught off South Africa was surveyed. A total of seven parasite taxa, including four new infection records (Bolbosoma capitatum, Rhadinorhynchus sp., Hepatoxylon trichiuri and Anisakis sp.), two new locality records (B. capitatum and Rhipidocotyle sp.) as well as the ectoparasitic copepod Sagum foliaceus and the cestode Tentacularia coryphaenae were recovered from the eight specimens examined.     

The life-cycle and seasonal abundance of Echinoparyphium montgomeriana n. sp. (Trematoda: Echinostomatidae) in Natal,South Africa

A new species of Echinoparyphium, E. montgomeriana, is described from Durban, South Africa. Certain unusual aspects of its morphology are discussed. The adult fluke is a parasite of the alimentary tract of birds. Its larval stages are common parasites of freshwater snails belonging to the family Planor-bidae including Buiinus africanus,the intermediate host ofSchistosoma haematobium and S. mattheei in the area. These intra-molluscan stages are shown to have a seasonal transmission cycle.     

Efficacy of condensed tannins against larval Hymenolepis diminuta (Cestoda) in vitro and in the intermediate host Tenebrio molitor (Coleoptera) in vivo

Natural anti-parasitic compounds in plants such as condensed tannins (CT) have anthelmintic properties against a range of gastrointestinal nematodes, but for other helminths such effects are unexplored. The aim of this study was to assess the effects of CT from three different plant extracts in a model system employing the rat tapeworm, Hymenolepis diminuta, in its intermediate host, Tenebrio molitor. An in vitro study examined infectivity of H. diminuta cysticercoids (excystation success) isolated from infected beetles exposed to different concentrations of CT extracts from pine bark (PB) (Pinus sps), hazelnut pericarp (HN) (Corylus avellana) or white clover flowers (WC) (Trifolium repens), in comparison with the anthelmintic drug praziquantel (positive control). In the in vitro study, praziquantel and CT from all three plant extracts had dose-dependent inhibitory effects on cysticercoid excystation. The HN extract was most effective at inhibiting excystation, followed by PB and WC. An in vivo study was carried out on infected beetles (measured as cysticercoid establishment) fed different doses of PB, HN and praziquantel. There was a highly significant inhibitory effect of HN on cysticercoid development (p = 0.0002). Overall, CT showed a promising anti-cestodal effect against the metacestode stage of H. diminuta.     

Heat tolerance of Boran and Tuli crossbred steers.

Experiments were conducted to evaluate the heat tolerance of the following breeds: Hereford (H), Brahman (B), H x B, H x Boran (H x Bo), and H x Tuli (H x T). Heat tolerance was evaluated in a climatically controlled room (Exp. 1) and under summer environmental conditions (Exp. 2) by comparing rectal temperatures (RT), respiration rates (RR), and sweating rates (SW). In Exp. 1, under extremely hot conditions (mean temperature-humidity index [THI] > 90), purebred B had significantly (P < .05) lower RT and RR than other genotypes, which may be indicative of greater surface area per mass to dissipate heat and a lower metabolic rate than other genotypes. Boran and Tuli crosses had RT (39.5 degrees C) that were intermediate to those of B (39.0 degrees C) and H x B (40.0 degrees C). The H genotype had the greatest RT at 40.3 degrees C. Among the breeds, trends in RR were similar to RR observed at THI < 77; B had the lowest RR, and H x B were intermediate. However, in these extreme conditions, RR did not differ among the purebred H and the Boran and Tuli crossbred steers, but H x B steers had lower RR than the other H crossbred steers. Sweating rates were significantly greater for the Bos indicus x Bos taurus crosses (H x B and H x Bo) than for the purebred genotypes (H and B) and the Bos taurus cross (H x T). In Exp. 2, mean RT for B, H x B, H x Bo, and H x T were very similar to those recorded under the moderate heat stress conditions found in Exp. 1. There were no differences in RT among B, H x Bo, and H x T genotypes. The RR increased over time for H only, and RR for other genotypes tended to be elevated only slightly over time. Among genotypes, SW was significantly greater for the H x Bo steers. The ability of the Bos indicus crosses to dissipate heat through enhanced SW and associated evaporative cooling was evident. However, the heat-tolerant nature of the Bos taurus cross (H x T) was not evident through enhanced RR or SW in either experiment. Compared with other genotypes, the lower RR of B steers was clearly evident and is assumed to be due to greater surface area and other skin characteristics that allow them to dissipate heat to maintain lower RT. These data suggest that the H x Bo and H x T are similar to H x B and intermediate to H and B genotypes in maintaining homeostasis when exposed to a high heat load.     

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.