Isoenzyme electrophoresis of 30 isolates of Giardia from humans and felines

Thirty isolates of Giardia duodenalis from humans and felines were compared by isoenzyme electrophoresis. Using 10 enzyme systems, 13 different zymodemes were distinguished. The majority of zymodemes could be divided into two groups: one group comprising human and feline isolates with worldwide geographic distribution; the other group containing human isolates restricted to Western Australia. A number of isolates showed multiple-banded patterns and the genetic significance of these findings is discussed. The marked heterogeneity of G. duodenalis demonstrated in this study is considered in relation to the epidemiology of giardiasis. The findings are consistent with felines serving as a reservoir of infection to humans

Fish out of water: Aquatic parasites in a drying world

Although freshwater ecosystems are among the most diverse and endangered in the world, little attention has been paid to either the importance of parasitic disease as a threatening process for freshwater organisms, or the co-extinction risk of freshwater parasites. In this review, we use theoretical and empirical studies of host/parasite interactions to examine these issues, particularly with respect to the threat posed by climate change to fish and parasite communities in intermittent rivers. Intermittent rivers are those that cease to flow at any point in time or space, with isolated pools providing ecological refuges for freshwater biota between streamflow events. Intermittent rivers are the dominant river type in arid, semi-arid and Mediterranean regions; areas of the world that have experienced dramatic decreases in streamflow as a result of climate change. Reduced streamflow decreases the number, size and connectivity of refuge pools in intermittent rivers, with important consequences for free-living aquatic organisms, particularly fishes, and their parasitic fauna. As a result of more frequent and sustained periods of no flow, parasite diversity within refuge pools is expected to decrease, with a concomitant increase in the prevalence and intensity of those parasite species which do survive, particularly host generalists. Decreased connectivity between refuge pool communities should increase the spatial modularity of host/parasite interactions, leading to a greater structuring of host and parasite communities along the river. This increases the probability of species loss (for both hosts and their parasites), as local extinctions cannot be reversed by colonisation from other localities

MITOCHONDRIAL DNA POLYMORPHISMS AND FERTILITY IN BEEF CATTLE

Two regions of mitochondrial DNA, D-loop and ND-5 were characterized using polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) involving 422 beef cattle of Hereford and composite breeds from Wokalup’s research station. ANOVA models (model I, II) were used to estimate associations between molecular haplotypes and quantitative traits. The phenotypic data used were records on calving rate, defined as the mean number of live calves born over four years, while the genotypic data used were the result of PCR-RFLP analysis in both regions of mitochondrial DNA using 7 restriction enzymes. The results of the present study have provided evidence that mitochondrial polymorphisms in the D-loop and ND-5 regions are associated significantly with fertility. This is the first report of a correlation between mitochondrial polymorphism in D-loop and ND-5 on fertility in beef cattle. Key words: PCR-RFLP, bovine mitochondrial DNA, D-loop, ND-5

Is Toxoplasma gondii a threat to the conservation of free-ranging Australian marsupial populations?

It has often been asserted that Australian marsupial species are particularly susceptible to Toxoplasma gondii infection and to clinical toxoplasmosis following infection. This implicates T. gondii as a potential threat to marsupial population viability, and contrasts to what is known of T. gondii in populations of several other host species. We reviewed the literature, and found a lack of scientifically robust evidence addressing the occurrence of T. gondii infection in free-ranging populations of Australian marsupial species, and the impacts of the infection on population health. Key limitations included a lack of studies in free-ranging marsupial populations, study findings susceptible to substantial chance influences, and selection, misclassification and confounding biases. The lack of scientifically robust data available on this topic indicates that assertions that free-ranging populations of Australian marsupials are particularly susceptible to T. gondii infection and to toxoplasmosis are premature. The threat of T. gondii to the viability of free-ranging marsupial populations should therefore be regarded, at this stage, as a hypothesis

A comparison of the palatability of racemic praziquantel and its two enantioseparated isomers in yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

The bitterness of racemic praziquantel (Rac-PZQ) constrains its use as an in-feed treatment against monogenean flukes in finfish aquaculture. Evidence exists in mammals that the R-(-) enantiomer of PZQ is less bitter than the S-(+) enantiomer. If fish exhibit this same response, then the recently described techniques for the large-scale resolution of R-(-)-PZQ from Rac-PZQ could facilitate the wide-spread application of this effective anthelmintic compound via feed. The hypothesis that yellowtail kingfish Seriola lalandi would find R-(-)-PZQ more palatable than Rac-PZQ and S-(+)-PZQ was tested in four trials. During the first three trials, the palatability of diets top-coated with 10 g kg-1 of Rac-PZQ or its two enantioseparated isomers were compared in small (85-160 g) and large (1.2 kg) yellowtail kingfish. A fourth trial compared the palatability of R-(-)-PZQ and Rac-PZQ at dietary inclusion levels of 2.5, 5.0 and 10.0 g kg-1 in small yellowtail kingfish (170 g). Ingestion data showed that R-(-)-PZQ to be no more palatable than either Rac-PZQ or S-(+)-PZQ to yellowtail kingfish, regardless of size. Indeed, evidence suggested that the S-(+)-PZQ to be slightly more palatable than both R-(-)-PZQ and Rac-PZQ. From these data, we hypothesize that the strong smell of R-(-)-PZQ (which was not present in S-(+)-PZQ) is an equally important determinant to palatability as taste in yellowtail kingfish. Results demonstrate that dietary inclusion level is a more important determinant to palatability than PZQ chirality; however, administration of R-(-)-PZQ may still be advantageous if it is demonstrated to be the only enantiomer efficacious against monogeneans

Factors influencing the development and carbohydrate metabolism of Echinococcus granulosus in dogs

Echinococcus granulosus adult worms, 35 days postinfection, were measured for dispersion in the intestines of 10 dogs, a range of morphological characters, and the excreted end products of carbohydrate catabolism following 4 hr incubation in vitro. Most worms were found in the proximal sections of the small intestine, but the pattern of dispersion differed between dogs. Worm development varied both between dogs and between different regions of the small intestine of individual dogs. Overall there was a high level of variability with no simple patterns. Worm metabolism was related to worm development and, also independently, to local population density within the intestine. Larger, more mature worms produced less lactate and, at higher densities. worms tended to produce more acetate and succinate (pathways with a higher energy yield than lactate) and less ethanol. Thus, both more developed worms and high population density are associated with a shift from cytosolic to mitochondrial metabolism. The variation between worm populations along the small intestine along with the observed variation between worm populations from sibling dogs infected with genetically identical parasites suggests that the local host environment has a significant effect on parasite development

Eimeria spp. infecting quenda (Isoodon obesulus) in the greater Perth region, Western Australia

Parasites of wildlife inhabiting urbanised and peri-urban environments are of interest regarding wildlife population health, and also veterinary public health in the case of parasites that can also infect humans and domestic animals. This study aimed to: identify, and estimate the prevalence of, species of Eimeria parasitic in quenda (Isoodon obesulus) in the greater Perth region, Western Australia; 2) morphologically describe and genetically characterise a novel observed species of Eimeria as E. angustus; and 3) genetically characterise E. kanyana. Eimeria spp. prevalence was 76.1% (95% CI 64.9–84.5%), and four putative species of Eimeria were identified. Eimeria kanyana was identified infecting quenda for the first time, with a prevalence of 54.9% (43.4–66.0%). Eimeria quenda was less prevalent, at 7.0% (3.1–15.5%). The novel species E. angustus was present in 45.1% of sampled quenda (34.0–56.6%). A second novel morphotype of Eimeria was present in 2.8% of sampled quenda (0.9–9.7%). Mixed Eimeria spp. infections were present in 21/71 quenda (29.6%, 95% CI 20.2–41.1%). Molecular phylogenetic analyses of E. kanyana and E. angustus were conducted at the 18S rRNA and mitochondrial cytochrome oxidase loci. At both loci, two isolates identified as E. kanyana grouped in a phylogenetic clade with E. trichosuri. Five isolates identified as the novel E. angustus were most closely related to E. tropidura at the 18S locus. At the COI locus, no sequence data were available for E. tropidura; isolates of E. angustus grouped with E. sciurorum

Haematozoa of wild catfishes in northern Australia

Very little is known about the diversity, prevalence, or pathogenicity of haematozoa in Australian freshwater fishes. Blood smears from 189 native catfishes, of six different species, from northern Australia were examined for haematozoa. Haematozoan infections were observed only in fishes from Queensland, at an overall prevalence of 0.191 (95% CI = 0.134-0.265). Intraerythrocytic haemogregarines were present in Neoarius graeffei from the Brisbane River at a prevalence of 0.35 (0.181-0.567). Trypanosomes were present in Tandanus species from four rivers, at prevalences ranging from 0.111 (0.020-0.330) to 1 (0.635-1), and in N. graeffei from one river in Queensland, at a prevalence of 0.063 (0.003-0.305). The haematozoans observed appeared to have little impact on their hosts. Tandanus spp. were significantly more likely to be infected with trypanosomes, suggesting a high parasite-host specificity. This is the first widespread survey of wild Australian freshwater catfishes for haematozoa, resulting in the first report of haemogregarines from Australian freshwater fish, and the first report of trypanosomes from Neoarius graeffei and Tandanus tropicanus

The effect of reinfection and mixed Trypanosoma cruzi infections on disease progression in mice

The progression of Chagas disease (CD) varies significantly from host to host and is affected by multiple factors. In particular, mixed strain infections and reinfections have the potential to exacerbate disease progression subsequently affecting clinical management of patients with CD. Consequently, an associated reduction in therapeutic intervention and poor prognosis may occur due to this exacerbated disease state. This study investigated the effects of mixed strain infections and reinfection with Trypanosoma cruzi in mice, using two isolates from different discrete typing units, TcI (C8 clone 1) and TcIV (10R26). There were no significant differences in mortality rate, body weight or body condition among mice infected with either C8 clone 1, 10R26, or a mixture of both isolates. However, the parasite was found in a significantly greater number of host organs in mice infected with a mixture of isolates, and the histopathological response to infection was significantly greater in mice infected with C8 clone 1 alone, and C8 clone 1 + 10R26 mixed infections than in mice infected with 10R26 alone. To investigate the effects of reinfection, mice received either a double exposure to C8 clone 1; a double exposure to 10R26; exposure to C8 clone 1 followed by 10R26; or exposure to 10R26 followed by C8 done 1. Compared to single infection groups, mortality was significantly increased, while survival time, body weight and body condition were all significantly decreased across all reinfection groups, with no significant differences among these groups. The mortality rate over all reinfection groups was 63.6%, compared to 0% in single infection groups, however there was no evidence of a greater histopathological response to infection. These results suggest firstly, that the C8 clone 1 isolate is more virulent than the 10R26 isolate, and secondly, that a more disseminated infection may occur with a mixture of isolates than with single isolates, although there is no evidence that mixed infections have a greater pathological effect. By contrast, reinfections do have major effects on host survivability and thus disease outcome. This confirms previous research demonstrating spontaneous deaths following reinfection, a phenomenon that to our knowledge has only been reported once before