Old problems on a new playing field: Helminth zoonoses transmitted among dogs, wildlife, and people in a changing northern climate

Although surveillance is limited, indigenous residents at latitudes ranging from 53 to 73°N in Canada appear to have a higher occurrence of infection with some zoonotic parasites than the general population. Conversely, they are relatively naïve to other zoonotic parasites that have previously been unable to establish at northern latitudes. For those parasites that circulate among dogs, wildlife, and people, potential risk factors in the North include limited availability of veterinary services, presence of free-roaming dog populations, and consumption of locally harvested fish and wildlife. These regions are also experiencing some of the greatest impacts of climate change in North America, including increased temperature, precipitation, and frequency and severity of extreme weather. We review the current taxonomy, genetic diversity, host and geographic distributions, epidemiology and risk factors for 3 genera of helminths (Diphyllobothrium spp., Echinococcus spp., and Toxocara sp.) in Canada's North in order to identify climate-sensitive aspects of their ecology. Free-living stages of parasitic zoonoses endemic in the Arctic (such as Diphyllobothrium dendriticum, the cervid strain of Echinococcus granulosus, and Arctic strains of Echinococcus multilocularis) will experience trade-offs between enhanced survival under wetter conditions and increased mortality under warmer conditions. Climate change might also lead to the introduction and establishment in the Arctic of parasitic zoonoses previously restricted to the sub-Arctic, such as Diphyllobothrium latum, Toxocara canis, and the prairie strain of E. multilocularis. Molecular techniques applied in broad geographic surveys are needed to address critical knowledge gaps in the geographic distribution, genetic diversity, and public health significance of zoonotic helminths already in the circumpolar North, and to determine the current barriers to range expansion of temperate-adapted parasites into the North. Dogs will continue to play important roles in the North, including that of a “bridging” host between sylvatic cycles and human communities. In a warming north, increased opportunities for business, agriculture, and tourism favor importation of dogs and their parasites into a newly suitable environment. Collaborations among veterinarians, public health personnel, and policy-makers are needed to enhance surveillance and mitigate for dog-transmitted parasitic zoonoses in a changing North.     

Baylisascariosis—Infections of animals and humans with ‘unusual’ roundworms

The nematode genus Baylisascaris (order Ascaridida, superfamily Ascaridoidea) contains nine relatively host-specific, parasite species of carnivores, omnivores, herbivores, carnivorous marsupials or rodents. They have a facultative heteroxenous life cycle, at least under experimental conditions. Eggs passed in faeces embryonate in the environment and the second-stage larva infective for both definitive and intermediate hosts develops. In intermediate hosts larvae migrate extensively through tissues, where they grow and moult to the third-stage, causing extensive damage. All Baylisascaris spp. are considered a potential cause of visceral, ocular and/or neural larval migrans in mammals including humans and in birds. This paper summarises our current knowledge on the prevalence, biology, pathogenicity and zoonotic significance of three Baylisascaris species: B. transfuga, B. schroederi and B. procyonis which have as definitive hosts bears, giant pandas and raccoons (occasionally dogs), respectively.     

Occurrence of Giardia and Cryptosporidium in pigs on Prince Edward Island, Canada

In a cross-sectional study of 633 pigs from 21 herds on Prince Edward Island, Canada (PEI), the prevalence of infection with Cryptosporidium and Giardia, and the genotypes and species of isolates were determined in order to establish the zoonotic potential of pigs in this region. As determined by direct immunofluorescence microscopy (DFA), 18 herds (86%) and 163 animals (26%; 95% CI: 22-29%) tested positive for Cryptosporidium, while just 3 herds (14%) and 6 animals (1%; 95% CI: 0.4-2%) tested positive for Giardia. Cryptosporidium spp. isolates were detected in 39% (95% CI: 34-44%) of weanlings (1-3 months of age) and 9% (95% CI: 6-13) of sows (>8 months of age). Molecular characterization using the 18S rDNA and HSP70 gene fragments revealed the presence of Cryptosporidium sp. pig genotype II, C. suis, C. parvum, and Cryptosporidium sp. mouse genotype. Among the 113 isolates of Cryptosporidium spp. successfully genotyped, pig genotype II (61%) predominated, with C. suis (36%) being the next most prominant isolate. C. parvum (2%; two isolates) and Cryptosporidium sp. mouse genotype (0.9%; one isolate) were only occasionally isolated. The only two Cryptosporidium-positive genotyped isolates from sows included one each of C. suis and Cryptosporidium sp. pig genotype II.All but one of the six Giardia positive isolates were detected in weanling pigs. None of the Giardia-positive isolates was amenable to PCR. This study demonstrates that Cryptosporidium spp. are highly prevalent in pigs on PEI, Canada, are found mostly in weanlings (1-3 months of age). Furthermore, the pigs are primarily infected by the host-specific genotypes and species, Cryptosporidium sp. pig genotype II and C. suis, whereas the zoonotic C. parvum is rare. Giardia duodenalis is only occasionally found in pigs. These findings suggest that domestic pigs on PEI, Canada, likely do not pose a significant health risk to humans from these parasites.     

Molecular detection of zoonotic tick-borne pathogens from ticks collected from ruminants in four South African provinces

Ticks carry and transmit a remarkable array of pathogens including bacteria, protozoa and viruses, which may be of veterinary and/or of medical significance. With little to no information regarding the presence of tick-borne zoonotic pathogens or their known vectors in southern Africa, the aim of our study was to screen for Anaplasma phagocytophilum, Borrelia burgdorferi, Coxiella burnetii, Rickettsia species and Ehrlichia ruminantium in ticks collected and identified from ruminants in the Eastern Cape, Free State, KwaZulu-Natal and Mpumalanga Provinces of South Africa. The most abundant tick species identified in this study were Rhipicephalus evertsi evertsi (40%), Rhipicephalus species (35%), Amblyomma hebraeum (10%) and Rhipicephalus decoloratus (14%). A total of 1634 ticks were collected. DNA was extracted, and samples were subjected to PCR amplification and sequencing. The overall infection rates of ticks with the target pathogens in the four Provinces were as follows: A. phagocytophilum, 7%; C. burnetii, 7%; E. ruminantium, 28%; and Rickettsia spp., 27%. The presence of B. burgdorferi could not be confirmed. The findings of this study show that zoonotic pathogens are present in ticks in the studied South African provinces. This information will aid in the epidemiology of tick-borne zoonotic diseases in the country as well as in raising awareness about such diseases in the veterinary, medical and tourism sectors, as they may be the most affected.     

The molecular epidemiology of Cryptosporidium and Giardia infections in coyotes from Alberta,Canada, and observations on some cohabiting parasites

Coyotes from southern Alberta and Saskatchewan, Canada, were examined for the presence of Giardia and Cryptosporidium and cohabiting helminths. Toxascaris was present in over 90% of the 70 animals examined, and Taenia sp. in 6.5–25% of the two groups of animals studied. Giardia (12.5–21.7%) and Cryptosporidium (0–17.4%) were also common and molecular characterisation revealed both zoonotic and host-adapted genotypes of Giardia, whereas the Cryptosporidium proved to be a variant of the canine species C. canis. The seasonal variation observed in the occurrence of Cryptosporidium may be related to stress-induced shedding of the parasite.     

Babesiosis in dogs and cats--expanding parasitological and clinical spectra

Canine babesiosis caused by different Babesia species is a protozoal tick-borne disease with worldwide distribution and global significance. Historically, Babesia infection in dogs was identified based on the morphologic appearance of the parasite in the erythrocyte. All large forms of Babesia were designated Babesia canis, whereas all small forms of Babesia were considered to be Babesia gibsoni. However, the development of molecular methods has demonstrated that other Babesia species such as Babesia conradae, Babesia microti like piroplasm, Theileria spp. and a yet unnamed large form Babesia spp. infect dogs and cause distinct diseases. Babesia rossi, B. canis and Babesia vogeli previously considered as subspecies are identical morphologically but differ in the severity of clinical manifestations which they induce, their tick vectors, genetic characteristics, and geographic distributions, and are therefore currently considered separate species. The geographic distribution of the causative agent and thus the occurrence of babesiosis are largely dependent on the habitat of relevant tick vector species, with the exception of B. gibsoni where evidence for dog to dog transmission indicates that infection can be transmitted among fighting dog breeds independently of the limitations of vector tick infestation. Knowledge of the prevalence and clinicopathological aspects of Babesia species infecting dogs around the world is of epidemiologic and medical interest. Babesiosis in domestic cats is less common and has mostly been reported from South Africa where infection is mainly due to Babesia felis, a small Babesia that causes anemia and icterus. In addition, Babesia cati was reported from India and sporadic cases of B. canis infection in domestic cats have been reported in Europe, B. canis presentii in Israel and B. vogeli in Thailand. Babesiosis caused by large Babesia spp. is commonly treated with imidocarb dipropionate with good clinical response while small Babesia spp. are more resistant to anti-babesial therapy. Clinical and parasitological cure are often not achieved in the treatment of small Babesia species infections and clinical relapses are frequent. The spectrum of Babesia pathogens that infect dogs and cats is gradually being elucidated with the aid of molecular techniques and meticulous clinical investigation. Accurate detection and species recognition are important for the selection of the correct therapy and prediction of the course of disease.     

A Multiplex Polymerase Chain Reaction Assay for Direct Detection and Differentiation of β-Hemolytic Streptococci in Clinical Samples from Horses

Streptococcus equi subspecies equi, S equi subspecies zooepidemicus, and S dysgalactiae subspecies equisimilis are β-hemolytic Streptococci, often isolated from horses with respiratory or genital diseases. The aim of this study was (i) defining and validating a multiplex polymerase chain reaction (PCR) protocol for identifying these Streptococci in bacterial cultures and for detecting them directly in equine clinical specimens, and (ii) defining and validating a cheap DNA extraction protocol for clinical specimens. When respiratory and genital samples from symptomatic and asymptomatic horses were tested by bacterial culture and by multiplex PCR, all the 150 samples culture-positive for S equi, S zooepidemicus, or S equisimilis were also positive by PCR. Of 150 culture-negative samples, 143 were negative by PCR. Seven samples were positive by PCR but negative by bacteriology. The multiplex PCR protocol described in this study is proven suitable for a sensitive, specific, and rapid detection and identification of S equi, S zooepidemicus, and S equisimilis in cultured bacterial colonies, as well as in clinical specimens from symptomatic or asymptomatic horses. The inclusion of internal control primers in the PCR protocol excludes false-negative results. A cheap DNA extraction method has been also validated for swabs, tracheal aspirates, bronchoalveolar lavage, and guttural pouches lavage samples.     

Role of pet dogs and cats in the transmission of helminthic zoonoses in Europe, with a focus on echinococcosis and toxocarosis

The close emotional tie between people and companion animals is a beneficial relation known as the human-animal bond. However, pet dogs and cats can play an important role in the transmission of helminthic zoonotic agents such as the tapeworms Echinococcus and the roundworms Toxocara which are directly transmitted from pets to the human environment without the involvement of vectors or intermediate hosts. In humans, echinococcosis has emerged in Europe and toxocarosis is still persisting in large endemic areas despite the availability of highly efficient anthelminthics for dogs and cats. Ecological changes significantly contributed to these trends: the high wild fox populations and the high density of freely roaming dogs and cats maintain a permanent infection pressure of these and other parasites. Further, the establishment of urban recreational environments closer to natural ecological systems boosted vole populations that represent urban reservoirs for zoonotic helminths. A good understanding of the parasites’ biology and epidemiology including the transmission to humans is required for planning and implementing effective prevention strategies. The continuous education of veterinarians and the information of the pet owners by providing uniform recommendations are of priority importance. A close collaboration between veterinary and public health professionals in a ‘One Health’ concept is required.     

Toxocara spp. infections in paratenic hosts

The zoonotic roundworms Toxocara canis and T. cati are not only present worldwide in their definitive hosts; they also frequently occur in other animal species, including humans. In those so-called paratenic hosts, the larvae do not develop into the adult stage, but rather migrate throughout the somatic tissue and persist as infectious L3 stage for extensive periods. Those arrested larvae may lead to severe inflammatory reactions and consequently to a wide range of pathological and clinical manifestations. However, the infected paratenic hosts also constitute a potential source of infection for the definitive hosts or humans who may also function as paratenic hosts. In the present review, current knowledge of larval migration in a variety of possible paratenic hosts is summarized including variations of migration routes and susceptibilities. Furthermore, information about the clinical and pathological changes for the presented species and possible consequences of the somatic migration of larvae, i.e. the resulting tissue damage as well as adverse host reactions to arrested larvae are reviewed. There are still many questions unanswered regarding larval behaviour in hosts other than their definitive host. Therefore, it is of great importance to continue further elaboration on the biology of Toxocara spp. to prevent further spreading of larvae in both the paratenic and the definitive host.     

Prevalence of Anaplasma,Bartonella and Borrelia Species in Haemaphysalis longicornis collected from goats in North Korea

North Korea is located on the northern part of the Korean Peninsula in East Asia. While tick-borne pathogens of medical and veterinary importance have been reported from China and South Korea, they have not been reported from North Korea. To screen for zoonotic tick-borne pathogens in North Korea, ticks were collected from domestic goats. A total of 292 (27 nymph, 26 male, 239 female) Haemaphysalis (H.) longicornis were collected and assayed individually for selected tick-borne pathogens. A total of 77 (26.4%) were positive for Anaplasma bovis, followed by Bartonella (B.) grahamii (15, 5.1%), Anaplasma phagocytophilum (12, 4.1%), Bartonella henselae (10, 3.4%), and Borrelia spp. (3, 1.0%) based on 16S ribosomal RNA and ITS species-specific nested polymerase chain reaction. Using the groEL-based nested PCR, a total of 6 and 1 H. longicornis were positive for B. grahamii and B. henselae, respectively. All products were sequenced and demonstrated 100% identity and homology with previously reported sequences from other countries in GenBank. This is the first report of the detection of tick-borne pathogens in the North Korea and suggests that farm animals may act as reservoirs for zoonotic tick-borne pathogens.     

Tularaemia: A challenging zoonosis

In recent years, several emerging zoonotic vector-borne infections with potential impact on human health have been identified in Europe, including tularaemia, caused by Francisella tularensis. This remarkable pathogen, one of the most virulent microorganisms currently known, has been detected in increasingly new settings and in a wide range of wild species, including lagomorphs, rodents, carnivores, fish and invertebrate arthropods. Also, a renewed concern has arisen with regard to F. tularensis: its potential use by bioterrorists. Based on the information published concerning the latest outbreaks, the aim of this paper is to review the main features of the agent, its biology, immunology and epidemiology. Moreover, special focus will be given to zoonotic aspects of the disease, as tularaemia outbreaks in human populations have been frequently associated with disease in animals.     

Phenotypic and genotypic characterization of Staphylococcus aureus isolated from raw camel milk samples

In the present study 320 milk samples collected from 160 apparently healthy camels of three different locations in Sudan were investigated for the presence of Staphylococcus aureus resulting in the isolation of this bacterial pathogen from 28 milk samples from 24 camels. Twenty-five S. aureus were identified phenotypically and by PCR mediated amplification of species-specific genes or gene segments. Investigation of the S. aureus for toxinogenic potential revealed that three S. aureus strains were positive for the enterotoxin encoding gene sec and the genes seg, sei, sem, sen and seo, representing the egc gene cluster. In addition all 25 S. aureus were positive for the superantigen-like encoding gene ssl7 (set1). Partial sequencing of gene sec of the three S. aureus strains yielded an almost complete sequence identity to the sequence of the sec variant sec2. However, all three sec2 genes of the present study showed a deletion of one base causing a frame shift and a corresponding earlier stop codon.According to the present results, the raw camel milk collected from three locations in Sudan seems to be, at least at this stage, of minor importance as vector causing staphylococcal food poisoning.     

A review of parasitic zoonoses in a changing Southeast Asia

Parasitic zoonoses are common and widely distributed in the Southeast Asian region. However, the interactions between parasites, hosts and vectors are influenced by environmental, socio-cultural and livestock production changes that impact on the distribution, prevalence and severity of disease. In this review we provide an update on new knowledge in the context of ongoing changes for the food-borne pig associated zoonoses Taenia solium and Trichinella spp., the food-borne trematodes Opisthorchis viverrini and Clonorchis sinensis, the water-borne trematodes Schistosoma spp., the vector-borne zoonotic protozoa Plasmodium knowlesi and Leishmania spp. and the soil-borne zoonotic hookworm Ancylostoma ceylanicum. These various changes need to be considered when assessing or developing regional control programs or devising new research initiatives in a changing SE Asia.     

Novel hemotropic Mycoplasma species in white-tailed deer (Odocoileus virginianus)

Globally, hemotropic Mycoplasma spp. are emerging or re-emerging zoonotic pathogens that affect livestock, wildlife, companion animals, and humans, potentially causing serious and economically important disease problems. Little is known about hemotropic Mycoplasma spp. prevalence, host-specificity, or route of transmission in most species, including wildlife. DNA amplification by PCR targeting the 16SrRNA and the RNaseP genes was used to establish the presence and prevalence of hemotropic Mycoplasma spp. in a white-tailed deer (O. virginianus) population in eastern North Carolina. Sixty-five deer (89%) tested positive for hemotropic Mycoplasma spp. where sequence analysis of the 16SsRNA and the RNaseP genes indicated the presence of at least three distinct species. This study represents the first detection of three distinct hemotropic Mycoplasma species in white-tailed deer and the first report of two novel hemotropic Mycoplasma species.     

Analysis of 16S rDNA sequences from pathogenic Leptospira serovars and use of single nucleotide polymorphisms for rapid speciation by D-HPLC

Leptospira have a worldwide distribution and include important zoonotic pathogens yet diagnosis and differentiation still tend to rely on traditional bacteriological and serological approaches. In this study a 1.3 kb fragment of the rrs gene (16S rDNA) was sequenced from a panel of 22 control strains, representing serovars within the pathogenic species Leptospira interrogans, Leptospiraborgpetersenii, and Leptospirakirschneri, to identify single nucleotide polymorphisms (SNPs). These were identified in the 5′ variable region of the 16S sequence and a 181 bp PCR fragment encompassing this region was used for speciation by Denaturing High Performance Liquid Chromatography (D-HPLC). This method was applied to eleven additional species, representing pathogenic, non-pathogenic and intermediate species and was demonstrated to rapidly differentiate all but 2 of the non-pathogenic Leptospira species. The method was applied successfully to infected tissues from field samples proving its value for diagnosing leptospiral infections found in animals in the UK.     

Population genetics of Toxoplasma gondii: new perspectives from parasite genotypes in wildlife

Toxoplasma gondii, a zoonotic protozoal parasite, is well-known for its global distribution and its ability to infect virtually all warm-blooded vertebrates. Nonetheless, attempts to describe the population structure of T. gondii have been primarily limited to samples isolated from humans and domesticated animals. More recent studies, however, have made efforts to characterize T. gondii isolates from a wider range of host species and geographic locales. These findings have dramatically changed our perception of the extent of genetic diversity in T. gondii and the relative roles of sexual recombination and clonal propagation in the parasite's lifecycle. In particular, identification of novel, disease-causing T. gondii strains in wildlife has raised concerns from both a conservation and public health perspective as to whether distinct domestic and sylvatic parasite gene pools exist. If so, overlap of these cycles may represent regions of high probability of disease emergence. Here, we attempt to answer these key questions by reviewing recent studies of T. gondii infections in wildlife, highlighting those which have advanced our understanding of the genetic diversity and population biology of this important zoonotic pathogen.     

Evaluation of the in vitro growth-inhibitory effect of epoxomicin on Babesia parasites

Epoxomicin potently and irreversibly inhibits the catalytic activity of proteasomal subunits. Treatment of proliferating cells with epoxomicin results in cell death through accumulation of ubiquinated proteins. Thus, epoxomicin has been proposed as a potential anti-cancer drug. In the present study, the inhibitory effects of epoxomicin on the in vitro growth of bovine and equine Babesia parasites were evaluated. The inhibitory effect of epoxomicin on the in vivo growth of Babesia microti was also assessed. The in vitro growth of five Babesia species that were tested was significantly inhibited (P < 0.05) by nanomolar concentrations of epoxomicin (IC₅₀ values = 21.4 ± 0.2, 4 ± 0.1, 39.5 ± 0.1, 9.7 ± 0.3, and 21.1 ± 0.1 nM for Babesia bovis, Babesia bigemina, Babesia ovata, Babesia caballi, and Babesia equi, respectively). Epoxomicin IC₅₀ values for Babesia parasites were low when compared with diminazene aceturate and tetracycline hydrochloride. Combinations of epoxomicin with diminazene aceturate synergistically potentiated its inhibitory effects in vitro on B. bovis, B. bigemina, and B. caballi. In B. microti-infected mice, epoxomicin caused significant (P < 0.05) inhibition of the growth of B. microti at the non-toxic doses of 0.05 and 0.5 mg/kg BW relative to control groups. Therefore, epoxomicin might be used for treatment of babesiosis.     

Comparison of in vivo and in vitro survival and fecundity rates of the poultry red mite, Dermanyssus gallinae

To assist in the testing of possible antigens in developing a vaccine against the poultry red mite (Dermanyssus gallinae De Geer), a rapid and reliable in vitro screening method is critical. This short paper describes how D. gallinae survival and fecundity rates in an in vivo feeding device compared to that of mites fed using an in vitro method. Results showed that survival of fed D. gallinae females and mites overall was greater in vitro, although there was no difference between male survival and fecundity between in vivo and in vitro designs. The in vitro feeding device described therefore has the potential to provide reliable results, comparable to those obtained by in vivo testing, to allow for the rapid screening of D. gallinae antigens.     

Prevalence of intestinal parasites and genotyping of Giardia intestinalis in pet shop puppies in east Japan

The current study examined the prevalence of intestinal parasites and genotypes of Giardia intestinalis in puppies from nine pet shops in east Japan. Fresh fecal samples from 1794 puppies (≦3 months old) were collected on one occasion. Giardia spp. was examined for specific coproantigen using ELISA kit (SNAP^®Giardia, IDEXX Laboratories, Inc., USA). Other intestinal parasites were detected microscopically using the formalin-ethyl acetate sedimentation technique. Genotyping was determined for the random 29 stool samples identified as Giardia spp. positive using PCR and direct sequencing of the glutamate dehydrogenase (gdh) gene. Overall prevalence of protozoan Giardia spp. and Cystoisospora spp. revealed 23.4% and 11.3%, respectively. Prevalence of ascarids, Strongyloides spp. and hookworms were recorded 1.8%, 1.1% and 0.1%, respectively. Protozoan Giardia spp. and Cystoisospora spp., thus, represent important pathogens among pet shop puppies. All genotyped G. intestinalis isolates were belonged to assemblage C or D, identified as dog-specific genotypes. Zoonotic assemblage A and B were not demonstrated. The result suggests that the risk of zoonotic transmission of G. intestinalis from pet shops puppies to humans may be quite low in Japan.