[show abstract][hide abstract] ABSTRACT: Cats, as definitive hosts, play an important role in the transmission of Toxoplasma gondii. To determine the seroprevalence and risk factors for T. gondii infection in Dutch domestic cats, serum samples of 450 cats were tested for T. gondii antibodies by indirect ELISA. Binary mixture analysis was used to estimate the seroprevalence, the optimal cut-off value and the probability of being positive for each cat. The seroprevalence was estimated at 18.2% (95% CI: 16.6-20.0%) and showed a decrease with age in very young cats, an increase up to about 4 years old and ranged between 20 and 30% thereafter. Hunting (OR 4.1), presence of a dog in the household (OR 2.1), former stray cat (OR 3.3) and feeding of raw meat (OR 2.7) were identified as risk factors by multivariable logistic regression analysis. Prevalence differences were estimated by linear regression on the probabilities of being positive and used to calculate the population attributable fractions for each risk factor. Hunting contributed most to the T. gondii seroprevalence in the sampled population (35%).
Preventive Veterinary Medicine 02/2012; 104(3-4):317-26. · 2.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this study was to examine the dynamics of parasite specific antibody development in Trichinella spiralis and Toxoplasma gondii co-infections in pigs and to compare these with antibody dynamics in T. spiralis and T. gondii single infections. In this experiment, fifty-four pigs were divided into five inoculated groups of ten animals, and one control group of four animals. Two groups were inoculated with a single dose of either T. gondii tissue cysts or T. spiralis muscle larvae, one group was inoculated simultaneously with both parasites and two groups were successively inoculated at an interval of four weeks. Specific IgG responses to the parasites were measured by ELISA. T. gondii burden was determined by MC-PCR carried out on heart muscle and T. spiralis burden by artificial digestion of diaphragm samples. Specific IgG responses to T. gondii and T. spiralis in single and simultaneously inoculated animals showed a respective T. gondii and T. spiralis inoculation effect but no significant interaction of these parasites to the development of specific antibodies with the serum dilutions used. Moreover, our data showed that the specific IgG response levels in groups of animals successively or simultaneously co-infected were independent of a respective previous or simultaneous infection with the other parasite. Additionally, no differences in parasite burden were found within groups inoculated with T. gondii and within groups inoculated with T. spiralis. Conclusively, for the infection doses tested in this experiment, the dynamics of specific antibody development does not differ between single and simultaneous or successive infection with T. gondii and T. spiralis. However, lower parasitic doses and other ratios of doses, like low-low, low-high and high-low of T. gondii and T. spiralis in co-infection, in combination with other time intervals between successive infections may have different outcomes and should therefore be studied in further detail.
[show abstract][hide abstract] ABSTRACT: Trichinella is an important foodborne pathogen causing considerable morbidity and mortality. To prevent human trichinellosis, meat inspection for Trichinella spp. at slaughter is a key instrument. Current testing is based on minimal infectious dose in humans, but a scientific basis for this approach is lacking. To this end, a dose-response model must be developed, allowing translation of exposure into disease burden at the population level. We developed novel methods for dose-response assessment using outbreak data incorporating sexual reproduction of the parasite. A selection of suitable outbreak studies, reporting numbers exposed and infected, as well as estimated doses, was collated from a literature study. Humans appear to be highly susceptible: exposure to low doses (few larvae) is associated with a considerable risk of infection. As a consequence, levels of Trichinella in meat must be low to maintain acceptable health risks.
Epidemiology and Infection 04/2011; 140(2):210-8. · 2.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: The association between helminth infections and childhood atopic diseases remains controversial. The majority of studies have been carried out in tropical areas, whereas less information is available from western countries with low intensity of helminth infections. In the Netherlands, the infection of pigs with Ascaris suum is very common, particularly on pig farms with outdoor facilities. This helminth can also infect humans, causing visceral larva migrans. This study aims at determining the prevalence of antibodies against A. suum and its association with allergic symptoms and sensitisation in a population of 4-year-old children living in The Netherlands. Blood samples from 629 children from the prospective birth cohort Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study were examined for Ascaris antibodies. Data on allergic symptoms and sensitisation were collected using questionnaires and radioallergosorbent tests (RAST). A total of 45 out of 629 (7%) were found to be Ascaris-seropositive. In addition, a positive association between Ascaris seropositivity and wheeze in the last year, doctor-diagnosed asthma and food and aero-allergen sensitisation was found. These results support the hypothesis that low-level or transient infection with helminths enhances allergic reactivity.
European Journal of Clinical Microbiology 08/2009; 28(11):1327-34. · 3.02 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper we evaluate serology as a tool to monitor Trichinella-free pig herds. Indoor, industrial-raised fattening pigs in the Netherlands are practically Trichinella-free, and were used as a negative reference cohort. A positive cohort was not available but we used sera from an endemic region in Argentina to model a plausible distribution of serological responses (as OD levels) in positive sera, employing the difference between the endemic sera and the negative Dutch sera. We describe a method for correcting for variation among ELISA plates using on-plate reference sera, and demonstrate how to apply these corrections to a collection of test sera from pig farms. The positive and negative reference distributions can be used to estimate fractions true and false positives, necessary for defining appropriate cutoffs to be used for classifying positive and negative animals. Based on this analysis, the serological test was shown to lack the predictive power required for its large scale deployment. The properties of the serological test were also compared to the conventional digestion assay, which is highly specific but considerably less sensitive.
[show abstract][hide abstract] ABSTRACT: We present the frequency and the nature of contact incidents of the Serotine bat, Eptesicus serotinus, with humans and with companion animals (specifically cats and dogs), in The Netherlands between 2000 and 2005. Out of 17 bats in bite contact with humans, five tested positive for European bat lyssavirus (EBLV) type 1a. Cats had the most numerous contacts with bats (49 times) but a relatively low number of these bats were EBLV positive (six times). We estimated that the average incidence of human bat rabies infection might be between once per year and once per 700 years, depending mainly on the number of infectious viral particles in bat saliva. The risk of bat rabies is higher between April and October, and in the northern half of the country. This is the first study in Europe describing the risk of human bat rabies after bat contact incidents.
Epidemiology and Infection 02/2008; 137(6):803-9. · 2.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis) is a protozoan organism that can infect the intestinal tract of many animal species including mammals. Genetic heterogeneity of G. duodenalis is well described but the zoonotic potential is still not clear. In this study, we analysed 100 Giardia DNA samples directly isolated from human stool specimens, to get more insight in the different G. duodenalis assemblages present in the Dutch human population. Results showed that these human isolates could be divided into two main Assemblages A and B within the G. duodenalis group on the basis of PCR assays specific for the Assemblages A and B and the DNA sequences of 18S ribosomal RNA and the glutamate dehydrogenase (gdh) genes. Genotyping results showed that G. duodenalis isolates originating from Dutch human patients belonged in 35% of the cases to Assemblage A (34/98) and in 65% of the cases to Assemblage B (64/98) whereas two human cases remained negative in all assays tested. In addition, we compared these human samples with animal samples from the Netherlands and human and animal samples from other countries. A phylogenetic analysis was carried out on the DNA sequences obtained from these Giardia and those available in GenBank. Using gdh DNA sequence analysis, human and animal Assemblage A and B Giardia isolates could be identified. However, phylogenetic analysis revealed different sub-clustering for human and animal isolates where host-species-specific assemblages (C, D, E, F and G) could be identified. The geographic origin of the human and animal samples was not a discriminating factor.
International Journal for Parasitology 07/2006; 36(7):849-58. · 3.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: The identification of sequence regions in the genomes of pathogens which can be useful to distinguish among species and genotypes, is of great importance for epidemiological, molecular, and phylogenetic studies. The 5S ribosomal DNA intergenic spacer region has been identified as a good target to distinguish among eight Trichinella species and genotypes. The recent discovery of two non-encapsulated species in this genus, Trichinella papuae and Trichinella zimbabwensis, which can infect both mammals and reptiles, has suggested analyzing their 5S rDNA. Amplification of the tandem repeats of the 5S rDNA intergenic region of encapsulated species of Trichinella shows a 751bp fragment, whereas the three non-encapsulated species show a fragment of 800bp with T. pseudospiralis showing an additional fragment of 522bp. Although the size of the 800bp PCR fragments of T. papuae and T. zimbabwensis are similar to that of T. pseudospiralis, there are differences in the 5S rDNA intergenic regions among the three non-encapsulated species. Phylogenetic analysis of the 5S rDNA intergenic regions shows a clustering together of the three non-encapsulated Trichinella species that is well separated from the encapsulated ones. In addition, a single PCR-based method allows distinguishing non-encapsulated and encapsulated species.
[show abstract][hide abstract] ABSTRACT: The prevalence of the fox tapeworm in foxes (final host) and muskrats (one of the intermediate hosts) in the Netherlands and Europe has been discussed. The tapeworm was found in 9.4% of the investigated foxes from the province of Groningen and in 0.2% of the muskrats from the same region. Also in the province of Limburg positive foxes were found, but no positive muskrats. Possible ways of infection for humans are described together with methods for prevention. It is concluded that at this moment risks for humans to become infected are minimal, but vigilance and monitoring of foxes and muskrats remains needed.
Tijdschrift voor diergeneeskunde 06/2002; 127(10):318-21. · 0.13 Impact Factor