Reproductive potential of Echinococcus multilocularis in experimentally infected foxes, dogs, raccoon dogs and cats

A total of 15 red foxes, 15 raccoon dogs, 15 domestic dogs and 15 domestic cats were each infected with 20,000 protoscolices of Echinococcus multilocularis. At 35, 63, and 90 days post inoculation (dpi), five animals from each group were necropsied and the worm burdens determined. The highest worm burdens in foxes (mean of 16,792) and raccoon dogs (mean of 7930) were found at 35 dpi. These declined to a mean of just 331 worms in foxes and 3213 worms in raccoon dogs by day 63 with a further decline to 134 worms in foxes and 67 worms in raccoon dogs by day 90. In dogs, there was no significant difference between worm burdens recovered at days 35 (mean of 2466) and day 90 (mean of 1563), although reduced numbers were recovered on day 63 (mean of 899). In cats, worms were found in four animals 35 dpi (mean of 642), in three at 63 dpi (mean of 28) and in two at 90 dpi (mean of 57). Faecal egg counts were determined at 3 day intervals from 25 dpi. A mathematical model of egg excretion dynamics suggested that the mean biotic potential per infected animal was high in foxes (346,473 eggs); raccoon dogs (335,361 eggs) and dogs (279,910 eggs) but very low for cats (573 eggs). It also indicated that approximately 114, 42 and 27 eggs per worm were excreted in the faeces of dogs, raccoon dogs and foxes, respectively. The fecundity of worms in cats was low with an average of less than one egg per worm. The peak levels of coproantigen were detected earlier in foxes and raccoon dogs than in dogs. Eggs recovered from foxes, raccoon dogs and dogs resulted in massive infections in experimental mice. However, metacestodes did not develop from eggs originating from infected cats. It is concluded that foxes, raccoon dogs and dogs are good hosts of E. multilocularis. In contrast, the low worm establishment, the very few excreted eggs and the lack of infectivity of eggs strongly indicate that cats play an insignificant role in parasite transmission.     

Population dynamics and epidemiology of Toxocara canis in Danish red foxes

Toxocara canis, an intestinal helminth of canids with zoonotic potential, was found in 618 (59%) of 1,040 red foxes (Vulpes vulpes) collected from all Danish provinces (1997-2002). The prevalence and average worm burden were significantly higher for cubs than older foxes and in males than in females. A multiple logistic regression demonstrated that the prevalence was influenced significantly by sex and age of foxes in addition to location, season, and year of collection. The highest prevalence and worm burden were found in rural areas. The size and number of female worms was positively correlated to the fecal egg excretion. The length and fecundity of the worms was significantly higher in male foxes, and a general intensity dependence was suggested from a negative correlation between worm numbers and worm lengths. As compared to intestinal recovery of worms, somatic larvae were recovered from 20% of muscle samples and fecal eggs in 41% of fecal samples. The consistent finding of T. canis larvae in somatic tissues of naturally infected foxes is new.     

Meriones meridianus and Lagurus lagurus as alternative definitive hosts of Echinococcus multilocularis and E. granulosus.

The utilization of Meriones meridianus and Lagurus lagurus as alternative definitive hosts for Echinococcus multilocularis and E. granulosus was investingated. Tapeworm stage development of E. multilocularis was observed and their recovery rate was determined in the small intestine of M. meridianus and L. lagurus. These were compared with those in golden hamsters, which are known as alternative definitive hosts. The animals were treated with PTBA (prednisolone tertiary butylacetate) and PA (prednisolone acetate), after which M. meridianus showed the highest recovery rate, whereas L. lagurus had few or no worms. The recovery rate of worms from golden hamsters was between those of M. meridianus and L. lagurus. On day 20 post-infection, developing tapeworms with mature segments were collected from M. meridianus treated with PA. The worms were mostly from the proximal and medial small intestine. The three species of animals infected orally with E. granulosus were divided into two groups, PTBA-treated and non-treated control groups. PTBA promoted/enhanced the recovery rate of the worms until 5 days, but none or only a few worms were found in PTBA treated animals thereafter. The highest recovery rate was obtained from M. meridianus treated with PTBA on day 5 post-infection. Some worm developments were observed on days 5 and 10 post-infection. These results demonstrate that M. meridianus could be useful as an alternative definitive host of Echinococcus.     

Experimental Oesophagostomum bifurcum in monkeys

OESOPHAGOSTOMUM BIFURCUM: larvae, cultured from human stools collected in northern Ghana, were used to establish experimental infections in monkeys. A patent infection was established in a rhesus monkey (Macaca mulatta) and this infection was used to generate larvae to inoculate additional monkeys. In all, 17 animals were inoculated. Thirteen of 15 animals developed antibodies to the infection between 19 and 62 days post inoculation (PI); two animals had a positive response before inoculation. Four of ten animals developed patent infections between 88 and 134 days and passed eggs in the faeces. Egg shedding was consistent in only one animal, but at low levels of one or two eggs per 2 mg direct smear, and extended over a 400 day period. In the other three animals, egg shedding was sporadic and of only 2-4 weeks duration. In seven animals necropsied between 19 and 22 days PI, one to 17 early fourth-stage larvae were recovered from nodules in the bowel wall; in an eighth animal examined at 314 days, six immature adult worms (early fifth stage) were recovered from nodules in the bowel wall. The morphological features and growth of these recovered larvae are described. Three animals were inoculated with larvae that had been dried for one week at 28 degrees C; two animals began shedding eggs at 128 and 134 days PI, respectively. The present results suggest that the parasite obtained from humans is poorly adapted to lower primate hosts, and supports the concept that Oesophagostomum bifurcum found in humans and monkeys in the same geographical region of northern Ghana and Togo are distinct and that the infections in humans are not likely to represent zoonotic infections acquired from monkeys.     

Contamination of fox hair with eggs of Toxocara canis

Eighty-seven red foxes were investigated for the presence of Toxocara eggs on a sample of their hair from the peri-anal region. The worm burden of Toxocara in each fox intestine was also assessed and the relationship between eggs on the hair and worms in the intestine explored. Twenty-eight per cent of the foxes were found to have Toxocara eggs on their hair, with an average of 1.31 +/- 3.21 eggs per gram of hair (+/- SD). Sixty-one per cent of foxes harboured Toxocara worms within their intestines, with a mean worm burden (+/- SD) of 4 +/- 8. Host age and sex did not significantly influence the observed eggs on the hair or the worm burden. No significant correlation was found between the numbers of eggs on the hair and the worm burden within the intestine. These data collected from foxes are explored in the context of data from stray dogs and the possible epidemiological differences are discussed.     

Angiostrongylus cantonensis: Rejection of pulmonary arterial transfers of lung stage worms

Experimental transfer of the lung stage worms of Angiostrongylus cantonensis was performed between permissive hosts (rats) and between permissive (rat) and nonpermissive hosts (guinea pigs and rabbits). These worms from rats were rejected when implanted into nonpermissive hosts. Unexpectedly, similar worms did not survive well even in permissive hosts; the majority of recipient rats did not have first-stage larvae (L₁) in their stools and, even when positive for L₁, the number of the larvae shed was few. These findings contrast with the successful pulmonary arterial transfer of younger, intracranial-stage worms. It was shown that differences in rat strain between donor and recipient had no significant effect on the subsequent worm survival in recipient hosts. The alteration of maintaining conditions of the intrapulmonary worms, prior to transfer, in terms of temperature, media, and maintaining period, also showed no profound effect on the subsequent worm survival. The kinetics of precipitating and reaginic antibody levels in rats implanted with the intrapulmonary worms were analogous to those in rats with intracranial-stage worms. The findings indicate that some qualitative differences may exist between the worms obtained from two different sites.     

The effect of cohabitation of Tubifex tubifex (Oligochaeta: Tubificidae) populations on infections to Myxobolus cerebralis (Myxozoa: Myxobolidae)

The competitive interactions between susceptible and resistant Tubifex tubifex (Oligochaeta: Tubificidae) exposed to Myxobolus cerebralis (Myxozoa: Myxobolidae) infections were investigated in two laboratory trials. Competition was assessed by the total parasite production over the course of the trials in mixed and pure cultures of M. cerebralis exposed worms, and by the genetic analyses of worms from the control and experimental groups at the beginning and end of the experiments. Mixed cultures of resistant and susceptible worms showed a 70% reduction in production of parasites released when compared with pure cultures of susceptible worms. In studies with laboratory and field-collected oligochaetes the mixed cultures at the end of the cohabitation experiments were dominated by resistant Tubifex from lineage V (HB strain) this strain of Tubifex has a competitive advantage over worms from other lineages. The results of this study suggest that certain species of Tubifex may be dead-end hosts to M. cerebralis by absorbing or inactivating the parasite and may also show greater survival compared to susceptible oligochaetes in certain whirling disease enzootic habitats.     

Persistent infection of Myxobolus cerebralis, the causative agent of salmonid whirling disease, in Tubifex tubifex

The objective of this study was to quantify and determine the periodicity in the release of the triactinomyxon (TAM) stage of Myxobolus cerebralis, the causative agent of salmonid whirling disease, by its aquatic oligochaete host Tubifex tubifex. For this, 24 individual T. tubifex (infected as a group at 15 C) were examined daily for the release of M. cerebralis TAMs, and the number of waterborne TAMs released by each worm was quantified. The duration of the infection in these worms was also monitored using a polymerase chain reaction (PCR) diagnostic test. TAMs were first released 74 days postexposure (PE) and continued to be released until 132 days PE. During this period, each worm released on average, 1.5 x 10(3) waterborne TAMs 12 times; however, no pattern or periodicity was noted. The results of the PCR diagnostic tests conducted at 5, 7, 9, and 15 mo PE were positive, and the persistent infection was confirmed at 606 days PE (approximately 20 mo) when the remaining worms began releasing TAMs again. Similar results were observed in naturally infected T. tubifex, indicating that these worms remain infected for the duration of their natural lifespan and are capable of shedding viable TAMs, in temporally separate periods. These findings open the possibility of a seasonal periodicity in TAM release by T. tubifex.     

The flea epifauna of a suburban fox (Vulpes vulpes) population

Five hundred and thirteen fleas, of eight different species, were collected from a sample of 252 foxes killed in suburban London. 25–8% of foxes carried fleas, with a mean of 204 fleas per fox. Levels of infestation of male and female hosts did not differ significantly. Possible sources of the fleas infesting foxes are discussed with respect to their seasonal occurrence and fox prey composition. No evidence was found to support the suggestion that foxes obtain the majority of their fleas from prey items, although occasional heavy infestations of some flea species were probably derived from recent meals. Although Pulex irritans, Paraceras m. melis and Ctenocephalides canis , which contributed 35 % of the flea epifauna, could be considered parasitic on the fox, it seems probable that foxes pick up the majority of their fleas from the habitat through which they move. Thus, two particularly heavily infested categories of foxes were found: (1) juveniles during July-September, their fleas probably being accumulated during exploratory and play activities, and (2) all animals during the period October-December.     

New records of nematomorph parasites (Nematomorpha: Gordiida) of ground beetles (Coleoptera: Carabidae) and camel crickets (Orthoptera: Rhaphidophoridae) in Washington State

From 1998 to 2003, beetles and crickets infected with hairworms were collected from 4 localities within the Hanford Nuclear Site and the Hanford Reach National Monument, located in a shrub-steppe region of Washington State along the Columbia River. Infected hosts comprised 6 species of carabid beetles within 5 genera and 2 camel crickets within 1 genus; all are newly documented insect-nematomorph associations. A large proportion of the infected hosts (48%) were collected from a single site during a single collecting period. Of the 38 infected hosts, 32 contained a single worm, 4 hosts contained 2 worms, and 2 hosts contained 3 worms. Five of the hosts with multiple infections contained at least 1 male and 1 female worm. Camel crickets were infected with Neochordodes occidentalis while carabids were infected with an undescribed species of Gordionus . As the majority of hairworms are collected in the post-parasitic adult phase, host data and hairworm-arthropod associations remain poorly documented and our work adds new data to this area of nematomorph biology.     

Dirofilaria immitis in coyotes and foxes in Missouri

Wild canid carcasses were obtained during the 1986-1987 and 1987-1988 trapping seasons in Missouri. Hearts and lungs from 293 coyotes (Canis latrans), 85 red foxes (Vulpes vulpes) and 70 gray foxes (Urocyon cinereoargenteus) were examined for Dirofilaria immitis. Age of hosts was determined by radiographic and histologic techniques. Nineteen coyotes (7%) had from 1 to 100 D. immitis and five red foxes (6%) had from 1 to 7 D. immitis, whereas gray foxes had none. This study indicates that heartworm prevalence differs by wild canid species within the same area and during the same time period.     

Population structure of two rabies hosts relative to the known distribution of rabies virus variants in Alaska

For pathogens that infect multiple species, the distinction between reservoir hosts and spillover hosts is often difficult. In Alaska, three variants of the arctic rabies virus exist with distinct spatial distributions. We tested the hypothesis that rabies virus variant distribution corresponds to the population structure of the primary rabies hosts in Alaska, arctic foxes (Vulpes lagopus) and red foxes (Vulpes vulpes) to possibly distinguish reservoir and spillover hosts. We used mitochondrial DNA (mtDNA) sequence and nine microsatellites to assess population structure in those two species. mtDNA structure did not correspond to rabies virus variant structure in either species. Microsatellite analyses gave varying results. Bayesian clustering found two groups of arctic foxes in the coastal tundra region, but for red foxes it identified tundra and boreal types. Spatial Bayesian clustering and spatial principal components analysis identified 3 and 4 groups of arctic foxes, respectively, closely matching the distribution of rabies virus variants in the state. Red foxes, conversely, showed eight clusters comprising two regions (boreal and tundra) with much admixture. These results run contrary to previous beliefs that arctic fox show no fine‐scale spatial population structure. While we cannot rule out that the red fox is part of the maintenance host community for rabies in Alaska, the distribution of virus variants appears to be driven primarily by the arctic fox. Therefore, we show that host population genetics can be utilized to distinguish between maintenance and spillover hosts when used in conjunction with other approaches.     

Surveillance and management of Echinococcus multilocularis in a wildlife park

The fox tapeworm Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a severe zoonotic disease that may be fatal if untreated. A broad spectrum of mammalian species may be accidentally infected even in captivity. In April 2011, liver lesions due to E. multilocularis were observed during the necropsy of a captive-born nutria (Myocastor coypus) in a French wildlife park, leading to initiation of a study to survey the parasite's presence in the park. A comparable environmental contamination with fox's feces infected by E. multilocularis was reported inside (17.8%) and outside (20.6%) the park. E. multilocularis worms were found in the intestines of three of the five roaming foxes shot in the park. Coprological analyses of potential definitive hosts in captivity (fox, lynx, wildcat, genet, wolf, bear and raccoon) revealed infection in one Eurasian wolf. Voles trapped inside the park also had a high prevalence of 5.3%. After diagnosis of alveolar echinococcosis in a Lemur catta during necropsy, four other cases in L. catta were detected by a combination of ultrasound and serology. These animals were treated twice daily with albendazole. The systematic massive metacestode development and numerous protoscoleces in L. catta confirmed their particular sensitivity to E. multilocularis infection. The autochthonous origin of the infection in all the captive animals infected was genetically confirmed by EmsB microsatellite analysis. Preventive measures were implemented to avoid the presence of roaming foxes, contact with potential definitive hosts and contaminated food sources for potential intermediate hosts.     

The effect of praziquantel on Schistosoma mansoni.

3 x 10(-6)M praziquantel fails to completely paralyse miracidia and cercariae in a short time but they are not infective when maintained in the solution. 3 x 10(-5)M praziquantel prevents infected snails shedding cercariae but does not kill daughter sporocyts or developing cercariae. As the action of praziquantel on adult worms is not blocked by 10(-2)M mecamylamine, pempidine or carbachol, but is reduced by calcium depletion, it is suggested that praziquantel may act by permitting calcium influx to muscle cells causing them to contract.     

Effect of host feeding and available glucose on glycogen synthase and phosphorylase activities in Hymenolepis diminuta and Vampirolepis microstoma

The influences of host feeding and the availability of glucose in vitro on the activities of glycogen synthase and glycogen phosphorylase in Hymenolepis diminuta and in Vampirolepis microstoma were studied. The worms were recovered from hosts that had been fed ad libitum, starved for 24 hr, or starved 24 hr and then refed for 1 hr immediately prior to worm recovery. The ratios of active to inactive glycogen synthase and phosphorylase were correlated with the host feeding regimen prior to recovery. Glycogen synthase in H. diminuta was predominately in the inactive D form in worms from both fed and fasted hosts. One hour after refeeding, up to 80% of the synthase was in the active I form. Phosphorylase in H. diminuta was predominantly in the active a form in worms from fed and fasted hosts, but activity of this enzyme was suppressed in worms from refed hosts. When H. diminuta from fasted hosts was incubated in a balanced salt solution containing 40 mM glucose, glycogen synthase I increased, and phosphorylase a decreased. Glycogen synthase in V. microstoma was predominantly in the inactive D form in worms from both the fed and fasted hosts, but the proportion in the active I form increased to over half the total synthase by 1 hr of host refeeding. The proportion of glycogen phosphorylase a was high in worms from fed hosts and decreased, but not dramatically, in worms from fasted hosts. The results suggested that the worms had access to another source of glucose, probably from the host bile, and we measured a low but significant concentration of carbohydrate in the gall bladder bile of mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Possible vector dissemination by swift foxes following a plague epizootic in black-tailed prairie dogs in northwestern Texas

To determine whether swift foxes (Vulpes velox) could facilitate transmission of Yersinia pestis to uninfected black-tailed prairie dog (Cynomys ludovicianus) colonies by acquiring infected fleas, ectoparasite and serologic samples were collected from swift foxes living adjacent to prairie dog towns during a 2004 plague epizootic in northwestern Texas, USA. A previous study (1999-2001) indicated that these swift foxes were infested almost exclusively with the flea Pulex irritans. Black-tailed prairie dogs examined from the study area harbored only Pulex simulans and Oropsylla hirsuta. Although P. irritans was most common, P. simulans and O. hirsuta were collected from six swift foxes and a single coyote (Canis latrans) following the plague epizootic. Thus, both of these canids could act as transport hosts (at least temporarily) of prairie dog fleas following the loss of their normal hosts during a plague die-off. All six adult swift foxes tested positive for antibodies to Y. pestis. All 107 fleas from swift foxes tested negative for Y. pestis by mouse inoculation. Although swift foxes could potentially carry Y. pestis to un-infected prairie dog colonies, we believe they play only a minor role in plague epidemiology, considering that they harbored just a few uninfected prairie dog fleas (P. simulans and O. hirsuta).     

First report of Trichinella nativa in red foxes (Vulpes vulpes schrencki) from Otaru City, Hokkaido, Japan.

Forty-three red foxes (Vulpes vulpes schrencki) and nine raccoon dogs (Nyctereutes procyonoides viverrinus) were captured in Otaru City, Hokkaido, Japan and examined by muscle digestion for the presence of Trichinella sp. larvae. Of the foxes, five (11.6%) were positive for larvae of Trichinella nativa while none of the raccoon dogs were found to be positive. This finding suggests that the red foxes are important reservoir hosts of sylvatic trichinellosis in Otaru, Hokkaido. This is the first report on Trichinella nativa in wild red foxes of Hokkaido, Japan.     

Host-parasite interface of Paratenuisentis ambiguus (Eoacanthocephala) in naturally infected eel and in laboratory-infected sticklebacks and juvenile carp and rainbow trout

Paratenuisentis ambiguus is described from natural infections in adult eels and from laboratory infections in sticklebacks and juvenile carp and rainbow trout. In captured eels, female worms kept reproducing in the laboratory for at least 1 mo. In the 3 small laboratory hosts female worms did not release eggs and longevity did not exceed 3-30 days. It is concluded that the small fishes were unsuitable final hosts. Worm penetration into the intestinal wall of all hosts was shallow. Thus, the small fishes also proved to be unsuitable paratenic hosts. The worms ruptured the intestinal mucosa and the underlying tunica propria and they often seemed to change their sites of attachment. The proboscides carried an osmiophilic surface coat that seemed to be supported by liquid drops from necrotic host tissue and by osmiophilic material apparently discharged from pores in the worm's proboscis hooks. The coat contained lipids, polysaccharides, and/or proteoglycans and likely other substances. Around the hooks the proboscis tegument harbored conspicuous cisternae of rough endoplasmic reticulum as is typical for cells with secretory function. Mostly, the worms were found with semi-invaginated proboscides. The resulting cavity inside the proboscis seemed to collect lipids and other remnants of host cells from the lesions caused by the worms. Whether the apical hollow might function as a gastric cavity is discussed.     

Enzooticity of the dogs,the reservoir host of Thelazia callipaeda,in Korea

The reservoir hosts of Thelazia callipaeda were examined. The eyes of the 76 dogs raised at farm. 78 military dogs (shepherds), 96 cattle, and 105 pigs were investigated for the presence of eyeworm. Among them, six worms of T. callipaeda were collected from two dogs raised at farm (2.7%), and 188 worms from 26 shepherds (33.5%). No worms were recovered from the cattle or pigs. These results suggest that the dogs, especially the military dogs are serving as a reservoir host of T. callipaeda in Korea.