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Neurocysticercosis is recognised as an important but neglected cause of epilepsy in developing countries where the parasite occurs. Data on the transmission dynamics of the parasite in endemic areas are scarce. Individuals living in these areas are likely to be highly exposed to the parasite, but relatively few of them develop active infections. The present study aimed to describe and gain insights into changes in antibody responses and infection patterns related to age and/or gender in a south Ecuadorian rural population by combining antibody and antigen serological data with demographic characteristics. In 25% of the population, antibodies to Taenia solium cysticerci were detected whilst 2.9% had circulating parasite antigens. The proportion of antibody-positive individuals increased significantly until the age of 40years to become stable in older individuals. A rule-based simulation model was developed to explain these variations and to reflect the dynamics of exposure to, and transmission of, the parasite. In contrast, the proportion of people presenting circulating parasite antigens, reflecting an active infection, was significantly higher in people older than 60years. Immunosenescence could explain such an observation since a weaker immune system in the elderly would facilitate the establishment and maintenance of viable cysticerci compared with fully immunocompetent younger individuals. This work points out the role of the immune system in the development of cysticercosis within an exposed population and highlights new essential issues in understanding the transmission dynamics of the parasite, its incidence and the resulting immunological response at a population level., (Copyright 2009 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

A molecular epidemiological study was conducted on 100 dairy (499 calves) and 50 beef (333 calves) farms in Belgium to estimate the prevalence of different Giardia duodenalis assemblages in calves younger than 10 weeks of age. Positive samples from the epidemiological study and from a previous clinical study were selected and genotyped based on the amplification of the beta-giardin gene. To investigate the occurence of mixed assemblage A and E infections in calves, a novel assemblage-specific PCR was developed based on the triose-phosphate isomerase gene. The prevalence was 22% (95% Probability Interval (PI): 12-34%) in dairy calves and 45% (95% PI: 30-64%) in beef calves. In total, 120 Giardia-positive samples from dairy and beef calves collected in the epidemiological study and from clinically affected calves were identified based on the amplification of the beta-giardin gene. Overall G. duodenalis assemblage E was more prevalent (in 64% of the samples), although the majority (59%) of the dairy calves were infected with G. duodenalis assemblage A. Furthermore, mixed G. duodenalis assemblage A and E infections were identified in 31% of the calf samples (n=101) using the assemblage-specific PCR. We believe this is the first report of mixed infections in calves, and the results of the present study indicate that calves, although mainly infected with the host-specific G. duodenalis assemblage E, are frequently infected with the zoonotic assemblage A, either as a mixed or mono-infection, suggesting that calves might be underestimated as a potential zoonotic reservoir for human infections.

The diagnostic performance of six foot-and-mouth disease (FMD) assays for detection of antibodies to the non-structural proteins (NSP) of the FMD virus (FMDV) was estimated using a Bayesian analysis on field sera from cattle of unknown infection status originating from post-FMDV outbreak situations in Israel and Zimbabwe. Estimations of the disease prevalence in both populations were also obtained. The diagnostic sensitivity estimates did not differ between both field studies, although overall Bayesian estimates were markedly higher than those previously reported based on sera from comparable experimentally infected (vaccinated) cattle populations. All NSP-based assays demonstrated a lower diagnostic specificity when applied to the Zimbabwean sera compared to both published specificities and similar Bayesian specificity estimates derived for the Israeli dataset. In Israel, the disease prevalence was estimated at 23.9% (95% credibility interval: 19.5-28.8%), whereas 65.4% (59.0-72.5%) was found in Zimbabwe. The need for reliable diagnostic test performance estimates and the benefits of Bayesian analysis in obtaining them are also addressed.

Sero-epidemiological surveys involving 27,526 cattle over a period of 8 years show that Theileria parva, the parasite causing East Coast fever (ECF) is found throughout southern Zambia. Higher values of T. parva sero-prevalence were observed in the plateau districts of Monze, Choma and Mazabuka than in the valley districts of Siavonga and Sinazongwe. Our results reveal a strong association between high T. parva sero-prevalence and the presence of the periodic climatic phenomenon known as the El Nino Southern Oscillation. More T. parva sero-positive samples were recorded during El Nino years (1997/98) (P<0.001) than other years in the study period. From this association, we conclude that Multiple El Nino Southern Oscillation Indices can be used to predict years with high or low ECF infection prevalence thereby contributing to the improved control of ECF in the area.

A Bayesian approach was used to determine both the test properties of three diagnostic test procedures and the prevalence of Giardia duodenalis in dairy calves in Belgium. A cross-sectional survey was conducted in the province of East Flanders, Belgium. Between September 2001 and December 2003, a total of 100 farms were visited and faecal samples were obtained rectally from 499 calves aged from newborn to 70 days. Because there is no gold standard for the diagnosis of a G. duodenalis infection in dairy calves, a subset of 235 samples obtained on the first 50 farms, was examined using three different assays: microscopical examination, an immunofluorescence assay (IFA) and an antigen detecting Elisa (ELISA). Based on the results of these three tests, Bayesian analysis indicated that the prevalence of G. duodenalis in dairy calves was 0.19 (95% Confidence Interval: 0.11-0.28) and that ELISA (Sensitivity (Se) 0.89 and Specificity (Sp): 0.90) and IFA (Se: 0.77 and Sp: 0.95) were both sensitive and specific diagnostic techniques, whereas microscopical examination was less sensitive (Se: 0.56 and Sp: 0.87). The proportion of positive farms was estimated as 0.42 (0.24-0.62). The prevalence and the cyst excretion in calves from different age categories were based on data obtained by IFA on all 499 samples. The prevalence was highest among four to five week old calves and remained high among older calves up to 10 weeks, but was lower among calves before the age of two weeks. The number of excreted cysts was estimated by IFA and ranged from 100 to 1,040,000 cysts per gram faeces, with a mean of 3516 cysts per gram faeces. The intensity of excretion peaked among four-week-old calves and remained high among calves up to the age of eight weeks. This is the first known study to use Bayesian analysis to estimate the prevalence of G. duodenalis in the faeces of dairy calves and to estimate test characteristics of diagnostic assays used for the detection of G. duodenalis.

Several diagnostic techniques are used to estimate the prevalence of the zoonotic tapeworm Taenia solium in pigs, but none of these tests are perfect, making interpretation of results difficult. A Bayesian approach was used to estimate values for the prevalence and diagnostic test characteristic of porcine cysticercosis by combining results of four imperfect tests. Village pigs (N = 868) slaughtered in Lusaka (Zambia), were bled, and tongue and routine meat inspected; and serum antibody and parasite antigen concentrations were determined by ELISA. A model, based on a multinomial distribution and including all possible interactions between the individual tests required 31 parameters to be estimated, but actually allowed only 15 parameters (i.e. had 15 degrees of freedom) to be estimated. Therefore, prior expert opinion on specificity and (in)-dependence of the tests was entered in the model, resulting in a reduction of the number of parameters to be estimated. The estimated prevalence of porcine cysticercosis was 0.642 (95% confidence interval 0.54-0.91). The performances of the tests were (sensitivity (se)-specificity (sp)): tongue inspection (se 0.210-sp 1.000), meat inspection (se 0.221-sp 1.000), Ab-ELISA (se 0.358-sp 0.917), Ag-ELISA (se 0.867-sp 0.947). To validate the estimates obtained from the model we performed a second study: 65 randomly purchased Zambian village pigs were bled for serum antibody and antigen determination, their tongue and meat inspected; and in addition, the carcasses were dissected for total cysticercus counts (gold standard). Cysticerci were found in 31 pigs (prevalence 0.477, 95% confidence interval 0.35-0.60), overlapping with the estimated prevalence in the first study. Sensitivity and specificity values obtained for the aforementioned tests in this study were in agreement with those estimated. A Bayesian analysis framework offers the possibility to combine prior opinion with experimental data to more accurately estimate the real prevalence of porcine cysticercosis in the absence of a gold standard.

Lyophilisation of Theileria parva sporozoite stabilates used for immunisation of cattle against East Coast fever would greatly improve vaccine storage and delivery. We report three attempts to lyophilise and resuscitate the sporozoites of T. parva. Sporozoites survived lyophilisation and were effective for immunisation. Lyophilised stabilate survived for 2 weeks at 5 degrees C and for 12 weeks at -20 degrees C. Although the viability of the stabilates was severely reduced during lyophilisation, this work suggests that this method has potential and should be considered for other Apicomplexan parasites such as Babesia sp. or Plasmodium sp.

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.