Dirk Berkvens

Bluetongue: Epidemiology in the European Union

Central and northern Europe are now at risk from bluetongue virus.

Evidence for genetic exchange and hybridization in Trypanosoma cruzi based on nucleotide sequences and molecular karyotype.

Trypanosoma cruzi is thought to undergo predominant clonal evolution, as determined by population genetics studies. However, this model does not exclude occasional recombination, which existence is strongly suggested by several recent studies. We sequenced a portion of the maxicircle cytochrome b (CYb) gene and of the nuclear rRNA promoter region from representative strains of six T. cruzi genetic lineages isolated from anthroponotic environments and man (lineages IIb, IId and IIe), sylvatic environments (lineages IIa and IIc) or both (lineage I). Phylogenetic analyses based on the two genes were incongruent. Remarkably, in lineage IIe, CYb and rRNA sequences were very closely related to those of lineages IIc and IIb, respectively. One stock of lineage IId showed rRNA sequence heterogeneity, with both IIb-like and IIc-like copies. Analysis of the size variation of six distinct pairs of putative homologous chromosomes revealed a bimodal distribution of chromosomal sizes across T. cruzi. Notably, stocks of lineages IId and IIe had several chromosomal pairs distributed in distinct modes, with the corresponding modes individually found in lineages IIb and IIc. Together, these data indicate the origin of lineages IId and IIe by hybridization between representatives of lineages IIb and IIc. CYb and rRNA sequences clustered into three and four major lineages, respectively. Data were in agreement with the distinction of six genetic lineages, but not with their proposed grouping into two primary lineages, as lineage II was not monophyletic. Based on a CYb substitution rate of 1% per million years (Myr), the major lineages are estimated to have diverged around 10 million years ago.

Sero-epidemiological study of Taenia saginata cysticercosis in Belgian cattle.

A sero-epidemiological survey of Taenia saginata cysticercosis was carried out to determine the prevalence of the infection in cattle presented for slaughter in Belgium. Between November 1997 and June 1998, a total of 1164 serum samples were collected in 20 export abattoirs. Meat inspection was routinely carried out by veterinary inspectors. Serum samples were examined for circulating parasite antigen using a monoclonal antibody-based sandwich enzyme-linked-immunosorbent assay (Ag-ELISA). Thirty six serum samples (3.09%) were found positive in the Ag-ELISA, while by meat inspection on the same animals cysticerci were detected in only three carcasses (0.26%). Sero-prevalence was positively correlated with the age of the animals. The sero-prevalence found in this study was more than 10 times higher than the annual prevalence (0.26%) reported by the Institute for Veterinary Inspection. This study clearly indicates that the classical meat inspection techniques detect only a minor fraction of the carcasses infected with cysticerci.

The Disease Burden of Taenia solium Cysticercosis in Cameroon

Background Taenia solium cysticercosis is an important zoonosis in many developing countries. Human neurocysticercosis is recognised as an important cause of epilepsy in regions where the parasite occurs. However, it is largely underreported and there is a lack of data about the disease burden. Because a body of information on human and porcine cysticercosis in Cameroon is becoming available, the present study was undertaken to calculate the impact of this neglected zoonosis. Methods Both the cost and Disability Adjusted Life Year (DALY) estimations were applied. All necessary parameters were collected and imported in R software. Different distributions were used according to the type of information available for each of the parameters. Findings Based on a prevalence of epilepsy of 3.6%, the number of people with neurocysticercosis-associated epilepsy was estimated at 50,326 (95% CR 37,299–65,924), representing 1.0% of the local population, whereas the number of pigs diagnosed with cysticercosis was estimated at 15,961 (95% CR 12,320–20,044), which corresponds to 5.6% of the local pig population. The total annual costs due to T. solium cysticercosis in West Cameroon were estimated at 10,255,202 Euro (95% CR 6,889,048–14,754,044), of which 4.7% were due to losses in pig husbandry and 95.3% to direct and indirect losses caused by human cysticercosis. The monetary burden per case of cysticercosis amounts to 194 Euro (95% CR 147–253). The average number of DALYs lost was 9.0 per thousand persons per year (95% CR 2.8–20.4). Interpretation This study provides an estimation of the costs due to T. solium cysticercosis using country-specific parameters and including the human as well as the animal burden of the zoonotic disease. A comparison with a study in South Africa indicates that the cost of inactivity, influenced by salaries, plays a predominant role in the monetary burden of T. solium cysticercosis. Therefore, knowing the salary levels and the prevalence of the disease might allow a rapid indication of the total cost of T. solium cysticercosis in a country. Ascertaining this finding with additional studies in cysticercosis-endemic countries could eventually allow the estimation of the global disease burden of cysticercosis. The estimated number of DALYs lost due to the disease was higher than estimates already available for some other neglected tropical diseases. The total estimated cost and number of DALYs lost probably underestimate the real values because the estimations have been based on epilepsy as the only symptom of cysticercosis.

Epidemiological survey of swine cysticercosis in two rural communities of West-Cameroon.

To determine the prevalence of porcine cysticercosis, a survey was carried out in 27 villages belonging to two rural communities of West-Cameroon (Bafou and Bamendou). Between January and August, 2000, a total of 707 pigs were examined serologically and by tongue inspection. Serum samples were examined for circulating parasite antigen using a monoclonal antibody-based sandwich enzyme-linked-immunosorbent assay (Ag-ELISA) and for antibodies against cysticerci (Ab-ELISA). Seventy eight samples (11.0%) were found positive in the Ag-ELISA and 154 (21.8%) in the Ab-ELISA, while by tongue inspection on the same animals cysticerci were detected in 43 pigs (6.1%). Gibbs sampling using results of these three tests indicated that the estimated prevalence of porcine cysticercosis was 10.9%. Analysis of the Ag-ELISA results demonstrated that adult pigs showed a significantly higher seroprevalence (15%) than young ones (8.4%). There was no statistical difference in cysticercosis prevalence in pigs raised in households with or without a latrine. Animals that were reported to be usually confined were significantly less infected (9.9%) than free-roaming pigs (16.2%). Infection rates were significantly higher in pigs that had access to human faeces (13.8%) than those which did not have access (9.1%). This study has identified some community behavioural and environmental practices that should be modified to prevent continuous transmission of porcine cysticercosis.

Pollen as an alternative food for Harmonia axyridis

The current study examines the potential of the multicoloured Asian lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) to use pollen as a food to sustain development and reproduction in the absence of insect prey. Three populations of H. axyridis were used in this study: a long-term laboratory population (since 1998) and a melanic and non-melanic population originating from field collected individuals in Belgium. The insects were allowed to develop and reproduce on frozen eggs of Ephestia kuehniella Zeller (Lepidoptera: Phycitidae), frozen moist bee pollen or an even mixture of the two. Females of the field population offered the mixed diet initiated oviposition sooner than those fed only E. kuehniella eggs, but other developmental and reproductive traits were similar on these diets. A diet of pollen alone allowed 35–48% of the larvae of the field population of H. axyridis to successfully reach adulthood. However, developmental time for these individuals was prolonged by 31–49% and adult body weight was reduced by 37–68%, compared to individuals offered the diets containing E. kuehniella eggs. When fed exclusively on pollen in their larval and adult life, about 40% of the adult females of either field population were able to produce a small number of viable eggs. The laboratory and field strains differed in their response to diet for a number of developmental and reproductive traits. The exploitation of pollen and other plant foods at times when insect prey is scarce, may offer a further competitive advantage to the non-indigenous coccinellid H. axyridis over native European predatory lady beetles that share the same niche and are less capable of using pollen as an alternative food.

Molecular epidemiology with subtype analysis of Cryptosporidium in calves in Belgium.

The prevalence of Cryptosporidium in calves younger than 10 weeks was estimated in a cross-sectional epidemiological study on 100 dairy (n=499) and 50 beef (n=333) farms in East Flanders (Belgium), using a previously evaluated immunofluorescence assay (Merifluor). The calf prevalence was 37% (95% Probability Interval (PI): 7-70%) in dairy calves and 12% (95% PI: 1-30%) in beef calves. To elucidate the genetic diversity, the Cryptosporidium 18S ribosomal DNA and the 70 kDa heat shock protein gene were targeted. In the majority of the samples C. parvum was present, although C. bovis was also identified, all but one in calves older than 1 month. The porcine-specific C. suis was identified in 1 beef calf. Subtyping of C. parvum positive isolates by sequence analysis of the 60 kDa glycoprotein gene indicated the presence of 4 allele IIa subtypes, along with 1 subtype IIdA22G1. The subtype IIaA15G2R1 was most prevalent, next to subtype IIaA13G2R1 and IIaA16G2R1, and a new subtype IIaA14G2R1. The results of the present study indicate a high prevalence of Cryptosporidium infections in calves in Belgium and confirm that these calves should be considered as a potential zoonotic reservoir for human infections.

Taenia solium cysticercosis in a village in northern Viet Nam: seroprevalence study using an ELISA for detecting circulating antigen

An enzyme-linked immunosorbent assay (ELISA) for detecting circulating Taenia solium antigen was evaluated in Viet Nam; 12 of 210 people gave a positive result, including 5 persons with epilepsy. Cysticercosis was confirmed in 9 persons. Agreement between the ELISA, computerized tomography scanning and biopsy examination was high.

Domestic animals and epidemiology of visceral leishmaniasis, Nepal.

Proximity of Leishmania donovani–positive goats is a risk factor for human infection.

Serological survey of Toxoplasma gondii, feline immunodeficiency virus and feline leukaemia virus in urban stray cats in Belgium

Three hundred and forty-six serum samples taken between 1998 and 2000 from urban stray cats in the city of Ghent were tested for antibodies to Toxoplasma gondii and feline immunodeficiency virus (FIV), and antigens of feline leukemia virus (FeLV). Of these 346 samples, 243 (70.2 per cent) were seropositive for T gondii. Thirty-nine cats (1 1.3 per cent) had antibodies againSt Flv and 13 (3.8 per cent) had circulating antigens Of FeLv. Fewer of the female cats had FIV and heavier cats had a higher seroprevalence Of FIV. Exact logistic regression showed that cats that were infected with FIV were more likely to be infected with T gondii (P=0.04), and the cats with Fivl had a higher titre of T gondii antibodies than Fill-negative animals. However, FeLV was not associated with either T gondii or FIV.