Population dynamics and host reactions in young foxes following experimental infection with the minute intestinal fluke, Haplorchis pumilio

Abstract

BackgroundInfections with fish-borne zoonotic trematodes (FZT) including the minute intestinal fluke, Haplorchis pumilio, are highly prevalent in Southeast Asia. However, little is known about the infection dynamics and clinical symptoms in the final hosts which include a range of animal species and man. We aimed to generate such information using an experimental model with H. pumilio in foxes.MethodEight commercially bred foxes were each orally infected with 2000 H. pumilio metacercariae. Another three foxes served as uninfected controls. Faecal examination for eggs was performed twice weekly. The body weight was measured, standard haematological and biochemical analysis were performed regularly. All foxes were euthanized at day 56 post infection (p.i.). Adult worms were quantified and location in the small intestine noted.ResultsAnorexia was observed in all infected foxes starting day 12 p.i. and lasting for approximately a week. A weight loss was noticed in the infected group in weeks 3–6 p.i. Five of eight infected foxes excreted H. pumilio eggs day 9 p.i. onwards, the remaining three started on day 13 p.i. Mean (± SD) faecal egg counts showed an initial peak at day 16–20 with a maximum of 1443 ± 1176 eggs per gram of faeces (epg), where after a stable egg output around 4–500 epg was seen. Worm burdens ranged between 116–2070 adult flukes with a mean (± SD) worm recovery of 948 ± 666. The majority of worms were found in the lower part of the jejunum. Total white blood cell and lymphocyte counts were significant lower in the infected group from first week p.i. onwards and throughout the study period. A significantly lower level of eosinophils was found in week 2 p.i. and transient anaemia was seen in week 2 and 4 p.i.ConclusionThis study showed a short prepatency period, an initial peak in egg excretion, establishment of infection in all animals with predilection site in the lower jejunum and a marked but transient clinical effect of the infection. The findings on egg output and prepatency should be taken into consideration when control programs targeting dogs and other reservoir hosts are to be established.

Environmental contamination with Toxocara eggs: a quantitative approach to estimate the relative contributions of dogs, cats and foxes, and to assess the efficacy of advised interventions in dogs

“…Prevalence was modelled as a Beta distribution (Table 1 ). The mean and standard deviation of the faecal output of foxes were provided by Nissen et al [ 42 ] so that the fox faecal output ( F 4 ) could be modelled as a log normal distribution (Table 1 ). EPG in foxes by age group ( I 4 j ) was obtained from Saeed et al [ 12 ] and modelled as a Poisson distribution (Table 1 ), with no changes over degrees of urbanization.…”

Testing of UK Populations of Culex pipiens L. for Schmallenberg Virus Vector Competence and Their Colonization

“…pipiens f. pipiens, even in the original field material) is highly likely to be representative of this form, results from the Brookwood line are more difficult to interpret. The fact that these lines and the additional Wageningen line originating from The Netherlands failed to support full SBV dissemination, however, would suggest that the presence of hybrids in tested populations does not substantially influence vector competence for SBV, in contrast to WNV [ 17 ]. Further studies to examine this issue directly with zoonotic pathogens would be useful in elucidating the potential role that these hybrids might play in arbovirus outbreaks in northern Europe.…”

“…It has been suggested that hybridization in Cx . pipiens may, alongside differences in host preference [ 16 ], drive transmission of West Nile virus (WNV; Flaviviridae , Flavivirus ) through hybrids possessing a greater vector competence [ 17 ]. The full characterization of individuals as specific forms or hybrids is therefore becoming an increasing important factor in studies [ 15 ].…”

Use of black carp (Mylopharyngodon piceus) in biological control of intermediate host snails of fish-borne zoonotic trematodes in nursery ponds in the Red River Delta, Vietnam

“…Including domestic animals in treatment campaigns would be a major challenge. At least for intestinal FZTs, the short life cycle [54] means that animals should be treated at frequency that is not logistically feasible. Hence farm/pond management [38] including stocking of ponds with black carp could well prove the major intervention to prevent infections in fish and people.…”