The prevalence of porcine cysticercosis in Eastern and Southern provinces of Zambia

The objective of this study was to determine the prevalence and importance of porcine cysticercosis in rural areas of Zambia. The study involved an abattoir survey of 1316 pigs at a slaughter slab in Lusaka and two field surveys in villages in Southern and Eastern provinces. Lingual examination of live pigs and visual inspection of their carcass as well as blood sampling for measuring circulating parasite antigen by enzyme-linked immunosorbent assay (Ag-ELISA) were used as parameters to measure infection. In the field surveys, a questionnaire was administered to every household whose pigs were examined to obtain information on pig husbandry practices and to study risk factors for the infection. Out of the 1316 pigs examined at the slaughter slab, 143 (10.9%) and 271 (20.6%) were positive by lingual examination and meat inspection, respectively. Most of the pigs were very heavily infected with predominantly live cysts. The field surveys revealed that eight (8.2%) out of 98 pigs from Southern province and eight (5.2%) out of 151 pigs from Eastern province were positive for cysticercosis by tongue palpation. Using the Ag-ELISA 20 (20.8%) and 14 (9.3%) pigs were positive in Southern and Eastern provinces, respectively. The questionnaire survey revealed poor pig husbandry practices, absence of meat inspection and control, poor knowledge of the disease and poor sanitation in the surveyed villages. The prevalence of pig cysticercosis found in this study ranks among the highest in the southern African region, in Africa and in the world. The current study suggests the presence of human tapeworm carriers and a high risk of human cysticercosis in the surveyed areas as well as in urban centres where pigs from rural areas are increasingly sold, slaughtered and consumed.     

Evidence that active transmission of porcine cysticercosis occurs in Venezuela

There is a paucity of quantitative data on the status of porcine cysticercosis in Venezuela, information which is essential for understanding the level of disease transmission. This study was, therefore, conducted in a typical small rural community in Yaracuy State, Venezuela, where previous cases of human Taenia solium taeniasis/cysticercosis had been reported and where the free-ranging pig management practices and the lack of rudimentary sanitary facilities indicated an obvious risk for transmission of the disease. Serum samples from 52 village pigs were screened by enzyme-linked immunosorbent assays for anti-cysticercal antibodies (Ab-ELISA), using T. solium cyst fluid as the antigen and the HP10, monoclonal antibody-based, antigen trapping ELISA for parasite antigen (HP10 Ag-ELISA). Significantly, a high proportion of the animals (65.4% for the Ab-ELISA and 42.3% for the HP10 Ag-ELISA) were sero-positive. Five of the pigs, which were selected on that basis of positive tongue palpation, were killed for autopsy, and large numbers of viable cysticerci were found in the carcases. This unequivocal documentation of porcine cysticercosis in Venezuelan pigs presents clear evidence that T. solium is actively transmitted in Venezuela. Further detailed studies and implementation of appropriate control measures are therefore indicated.     

A health-education intervention trial to reduce porcine cysticercosis in Mbulu District, Tanzania

We conducted a randomised community controlled trial to estimate the effectiveness of health and pig-management education intervention in reducing the incidence rate of porcine cysticercosis caused by Taenia solium in Mbulu District, northern Tanzania, between April 2002 and July 2004. We included a random sample of 827 pig-keeping households from 42 randomly selected villages in our 27-month study. We collected baseline data on the prevalence of porcine cysticercosis based on lingual examination of live pigs, and pig-management and sanitation knowledge and practices based on questionnaire interviews and observations. We allocated 21 of the villages to the health-education intervention, developed with community participation; we used stratified randomisation to balance the village-level baseline prevalence of porcine cysticercosis. From July 2003 to March 2004 following the intervention, we gave each participant household a sentinel piglet to raise (the timing was balanced between the intervention groups). Knowledge about the transmission and prevention of porcine cysticercosis was improved >42% in both groups when measured 10–12 months post-intervention. There was no improvement in observed practices in either group throughout the study period. However, the intervention had a significant reduction in the reported cases of household consumption of infected pork (a reduction by 20%). The intervention was associated with a considerable decrease in the incidence rate of porcine cysticercosis (incidence rate ratio 0.57) as measured by antigen-ELISA in sentinel pigs. Public education could lead to a reduction of the risk of infection in humans.     

Risk factors associated with porcine cysticercosis in selected districts of Eastern and Southern provinces of Zambia

To determine the risk factors associated with Taenia solium transmission in humans and pigs in the rural areas of Eastern and Southern provinces of Zambia, a questionnaire was administered in 788 households from 155 villages. Pigs were examined from 800 households. Tongue examination and enzyme-linked immunosorbent assay (Ag-ELISA) for the detection of circulating antigens of T. solium cysticerci were used to measure infection in pigs. A snowballing technique was utilised to select households with pigs. Prevalence of households with pigs infected with T. solium on tongue examination by district ranged from 12.7% to 32.1% with Ag-ELISA having a range of 30.0-51.7%. Of the total number of households visited, 18.8% and 37.6% had at least one pig positive for porcine cysticercosis on tongue examination and Ag-ELISA, respectively. Risk factors associated with T. solium infection were lack of pork inspection at slaughter (96.7%), consumption of pork with cysts (20.1%), selling of pork infected with T. solium cysticerci (18.3%), free-range husbandry system (83.2%) and absence of latrines (58.0). Free-range husbandry system (OR=1.68; 95% CI=1.36-2.07) was a significant risk factor for porcine cysticercosis in the surveyed areas. The result that pigs were mostly kept on free-range and semi-intensive husbandry systems may have permitted them to have access to eating human faeces that could be contaminated with tapeworm eggs. This study has shown that T. solium infection poses a high public health risk in the study areas and urban areas as well. We recommend that a human survey be conducted to verify the human exposure to taeniasis and/or cysticercosis in Zambia.     

PCR test for detecting Taenia solium cysticercosis in pig carcasses

Polymerase chain reaction (PCR) test was employed to detect Taenia solium DNA in muscle lesions for validation of the meat inspection results of slaughtered pigs. Two sets of oligonucleotide primers, one targeted against the large subunit rRNA gene (TBR primers) and the other targeted against cytochrome c oxidase subunit 1 gene (Cox1 primers) of T. solium were used in this study. On reactivity in PCR test, the TBR primers and the Cox1 primers yielded products of 286 and 984 bp, respectively, in cysticercosis positive cases. Both the sets of primers were found to be highly specific, since they did not yield any PCR product in negative controls. A total of 225 pig carcasses were screened for cysticercosis by meat inspection, out of which 25 carcasses with visible cysts (16 viable and 9 degenerated cysts) were also confirmed to be positive for cysticercosis in PCR test. However, out of the 35 carcasses with suspected lesions on meat inspection, only two were found to be positive for cysticercosis in PCR test. The detection limits for both the primer sets were analyzed. The TBR primer set could detect up to 10 pg of cysticercus DNA, whereas the Cox1 primer set could detect only up to 1 ng. It is evident from the study that PCR test is an efficient tool for validation of meat inspection results and also to rule out ambiguity in carcass judgment of suspected cases of porcine cysticercosis.     

Risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania

To estimate prevalence of and risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania, 770 live pigs were examined by lingual examination in 21 villages. Structured observations and questionnaire interviews were used to assess pig rearing practices and household use of latrines. Associations between factors were analyzed using a Bayesian hierarchical model to obtain prevalence odds ratio (OR) and 95% Bayesian Credible Intervals (95% BCI). Prevalence was 17.4% (village-specific range 3.2–46.7%). Prevalence of porcine cysticercosis was considerably higher in pigs reared in households lacking latrines than in those reared in households that were using latrines (OR=2.04; 95% BCI=1.25, 3.45). About 96% of the pigs were kept under free-range conditions. This study suggests the need for further studies in order to design and implement effective prevention and control measures for porcine cysticercosis in Mbulu District, Tanzania.     

The immune response in Taenia solium neurocysticercosis in pigs is associated with astrogliosis, axonal degeneration and altered blood–brain barrier permeability

Immunohistochemistry was used to examine the immuno-pathological changes and the extent of neuronal damage caused by either viable or dead Taenia solium cysticerci during porcine neurocysticercosis. Thirty pig brains with cerebral cysticercosis and 5 brains from T. solium free pigs were used in this study. Results revealed extensive astrogliosis, neuronal and mostly axonal damage in both early (grade I) and late (grades III and V) lesions as evidenced by an increased expression of glial fibrillary acidic protein (GFAP) and neurofilament protein (NFP). In many late lesions, astrocyte end-feet formed glial scars that surrounded the dead parasite. Rapid angiogenesis resulted in blood vessels lacking astrocyte end-feet suggesting loss of blood–brain barrier (BBB) hence allowing an influx of peripheral blood immune cells such as eosinophils, macrophages, CD3+ T cells, B lymphocytes and plasma cells into lesions. This study showed that porcine NCC was associated with severe nervous tissue damage, the host response of which is a collaborative effort between the local and peripheral immune responses comparable to that observed in human NCC. Results further implied that porcine NCC could be a useful model for understanding the course of NCC in human as well as provide useful information for therapeutic and/or immune strategies.     

Prevalence of extra-intestinal porcine helminth infections and assessment of sanitary conditions of pig slaughter slabs in Dar es Salaam city,Tanzania

A study was carried out to establish the prevalence of extra-intestinal porcine helminth infections and to assess the pig slaughter slab sanitary conditions in Dar es Salaam city, Tanzania. A total of 24 privately owned pig slaughter slabs were assessed. All slaughter slabs were sub-standard; wrongly located, poorly designed and constructed and lacked most basic requirements for a slaughter house. Because of inadequate slaughtering, disposal and cleaning facilities, the slaughter slabs were under unhygienic condition with questionable safety, soundness and wholesomeness of the pork produced. Routine meat inspection procedures were used to detect extra-intestinal porcine helminth infections. Of the 731 examined pigs; 8.1%, 5.9% and 0.4% were infected with ascariosis, porcine cysticercosis and hydatidosis, respectively. It was noted that almost all slaughter pigs in Dar es Salaam originated from different regions. Based on the region of origin, the status of porcine cysticercosis was 8.2% for Dodoma (n = 98), 8.2% for Manyara (n = 260) and 6.9% for Mbeya (n = 116). This study disclosed the unhygienic sanitary condition prevailing in Dar es Salaam pig slaughter slabs and recommends that strategies should be devised to improve the situation. Porcine ascariosis and cysticercosis were widely prevalent and caused economic losses due to condemnations. Because of their zoonotic nature, the observed extra-intestinal porcine helminth infections in pig pose a public health risk among consumers. Thus, there is a need to introduce appropriate control measures of parasitic infections in pigs.     

Emerging Trichinella britovi infections in free ranging pigs of Greece

Trichinella infections in humans and pigs have been documented in Greece since 1945 and a high prevalence of infection in pigs occurred in the 1950s. Up to 1984 only sporadic infections in humans were documented, and this zoonosis was not considered as a public health problem until 2009 when a human outbreak caused by the consumption of pork from an organic pig farm occurred. In the present study, we describe the re-emergence of Trichinella spp. infections in free-ranging pigs from organic farms of 3 counties (Dramas, Evros and Kavala) in Northern-Eastern Greece during the period 2009–2012. Totally 37 out of 12,717 (0.29%) free-ranging pigs which were tested during the period in question, were positive for Trichinella spp. larvae. The etiological agent was identified as Trichinella britovi. The average larval burden was 13.7 in the masseter, 6.2 in the foreleg muscles and 7.5 in the diaphragm. The 37 positive animals originated from seven free range pig farms. The practice of organic pig production systems in Greece has grown in popularity over the last years due to the increasing interest of consumers for products considered as traditional. However, this type of pig production increases the risk for Trichinella spp. infections, since animals can acquire the infection by feeding on carcasses or the offal of hunted or dead wild animals. The awareness and education of hunters and farmers is extremely important to reduce the transmission among free ranging pigs and the risk for humans.     

Validity of the Enzyme-linked Immunoelectrotransfer Blot (EITB) for naturally acquired porcine cysticercosis

The Enzyme-linked Immunoelectrotransfer Blot (EITB) has been used widely as a screening test for Taenia solium cysticercosis in swine. However, the relation between seropositivity and infection in pig populations from endemic areas has not been well defined. The aim of this study is to relate EITB seropositivity with infection and infection burden, analyse the trade-off between sensitivity and specificity with various cut-off points for the EITB assay, and finally describe the serology changes in a cohort of rural pigs raised under natural conditions. A group of 107 pigs that were used as controls during a vaccination field trial in Peru was our study population. The prevalence of porcine cysticercosis determined by necropsy examination was 16.82% (18/107) in these animals. Using EITB reactivity to ≥1 band as a cut-off point for the assay, the sensitivity was 88.89% (65.29–98.62, 95% CI) and the specificity was 48.31% (37.59–59.16, 95% CI). Comparing other cut-off points, involving up to as many as 7 reactive bands, a reactivity of ≥3 bands provided the best trade-offs in sensitivity and specificity. Using this cut-off point for the assay, the sensitivity was 77.77% (52.36–93.59, 95% CI) and the specificity was 76.40% (66.22–84.76, 95% CI). A significant association was found between cyst counts over 100 cysts and reactivity to ≥3 bands in the EITB assay (Fisher's exact test, p < 0.05). The results of this study suggest that the use of the EITB assay to study porcine cysticercosis may require setting different cut-offs under field and experimental conditions, and depending upon the objective of the screening process.     

Evaluation of the risk of transmission of Trichinella in pork production systems in Argentina

Recently, there has been interest in programs that certify pork production practices that minimize the risk of exposure of pigs to Trichinella spiralis. Certification might be useful for reducing the risk of human trichinellosis from pork in Argentina, but more information is needed on pig production practices and sources of Trichinella infection in Argentinian pigs. In this study, 21 pig farms were assessed for Trichinella infection including some farms using total and partial confinement management, and others with pigs raised exclusively outdoors. A total of 3224 muscle samples were collected from pigs raised on these farms and tested to determine the presence of T. spiralis larvae by artificial digestion. Serum samples from the same 3224 pigs were tested for antibodies to T. spiralis by ELISA. For each farm, a questionnaire was completed summarizing information about management factors and this information was used to assess risk factors for exposure of T. spiralis. Based on the results, pigs raised outdoors were more likely to be infected than pigs raised in total or partial confinement (p ≤ 0.05). Pigs fed waste products containing meat were 12.5 times more likely to be infected than pigs not fed waste containing meat (p < 0.01). The role played by rats in transmission of Trichinella is unclear; however, on farms with evidence of wild animals and access of pigs to wildlife carcasses, the prevalence of Trichinella infection was significantly higher. All pigs raised under good hygienic and sanitary conditions were negative for Trichinella infection by both artificial digestion and ELISA.     

Neurocysticercosis in free roaming pigs – a slaughterhouse survey

To investigate the prevalence of neurocysticercosis among free ranging pigs and to study the type of pathomorphological lesions in affected brains, a total of 200 brains were collected from pigs slaughtered at a local abattoir, between August, 2005 to March, 2006. Gross and histopathological examination revealed 3 % (6/200) occurrence of neurocysticercosis in pigs. Taenia solium cysticercosis is an under-rated zoonosis and is a leading cause of epilepsy due to neurocysticercosis in human population of India. The prevailing situation warrants immediate implementation of effective control measures for this dreaded disease.     

Epidemiological survey of swine cysticercosis using ante-mortem and post-mortem examination tests in the southern highlands of Tanzania

Pig keeping is known to be popular in the regions of the southern highlands zone (Mbeya, Iringa and Ruvuma) of Tanzania where more than 60% of pigs under the small-scale production system are raised. However, no epidemiological surveys on porcine cysticercosis have been conducted in the zone in spite of unofficial reports indicating the disease to be a widespread problem. To estimate prevalence rates and risk factors for porcine cysticercosis in Chunya and Iringa Rural Districts and Ruvuma Region (Songea and Mbinga Districts), 722, 808 and 302 live pigs, respectively, were examined by lingually and the prevalence of swine cysticercosis was found to be 7.6%, 8.4% and 16.9% for Chunya and Iringa Rural Districts, and Ruvuma Region, respectively. Structured observations and questionnaire interviews were used to analyse pig rearing practices and household use of latrines in Chunya and Iringa Rural Districts only. The analysis of effect of pig management practices, lack of a latrine, eating undercooked pork, home slaughter and no inspection of pork and lack of knowledge of T. solium on their association to tongue positivity in pigs was done by means of a contingency table. Odds ratios (OR) with corresponding 95% confidence intervals (95% CI) and p-values were calculated. Structured questionnaire interviews identified factors associated with the disease prevalence in both Chunya and Iringa Rural Districts were free-ranging of pigs, home slaughtering of pigs and pork not being inspected. While in Chunya and Iringa Rural Districts lack of latrine and barbecuing were found a risk factor, respectively. To control the disease in the study areas of the southern highlands there is a need for significant improvements regarding the use of latrines, confinement of pigs, pork inspection and thorough cooking of pork.     

Piloting the effectiveness of pig health education in combination with oxfendazole treatment on prevention and/or control of porcine cysticercosis,gastrointestinal parasites,African swine fever and ectoparasites in Angónia District,Mozambique

A community-based intervention combining health education (HE) and treatment of pigs for control of porcine cysticercosis (PC), gastrointestinal (GI) helminths, African swine fever (ASF) and external parasites was tested involving six villages of resource-poor smallholder pig farmers. Farmers and pigs of six rural villages were randomly allocated into group 1 (HE), which served as controls, and group 2 (HE?+?OFZ) pigs received a single oral dose of 30 mg/kg OFZ. Farmers were trained in pig health, housing and feeding. The proportion of farmers with confined pigs, the adoption rate of the introduced pig pen, the sero-prevalence of PC and ASF, the prevalence and intensity of GI nematodes and the prevalence of ectoparasites were measured at 9, 15 and 24 months after initiation and compared to a baseline survey to seek the effectiveness of the interventions. There was no clear effect of the intervention on the sero-prevalence of PC, but analysis of the rate of change in prevalence between the two groups showed significant effect with the rate of change to lower prevalence in the HE?+?OFZ group compared to the HE group. Although HE managed to improve the farmer’s knowledge in the control and prevention of ASF and ectoparasites, there was no significant reduction in the sero-prevalence of ASF and the prevalence of ectoparasites throughout the two-year period. The reported ineffectiveness of the intervention in this study suggested that more research is needed to develop more effective methods for controlling PC, ASF and pig parasites.     

Control of the taeniosis/cysticercosis complex: future developments

Cysticercosis is due to the establishment of the larval stage of the zoonotic cestode parasite Taenia solium. The infection causes substantial human morbidity and mortality, particularly in several Latin American countries and parts of Africa and Asia, as well as economic losses in pig husban dry due to condemnation of infected pork meat. The life cycle of T. solium includes human beings as definitive hosts and pigs as intermediate hosts. Cysticercosis is acquired by the ingestion of eggs released by human tapeworm carriers, who become infected after ingesting pork meat contaminated with cysticerci. Taenia solium transmission has been associated with poverty, lack of sanitary services and practices of rearing backyard pigs with free access to the areas that villagers use as toilets, as well as cultural behaviour. Nonetheless, due to the recent increase of migration and tourism, industrial countries are also reporting cases of human cysticercosis. There are many epidemiological studies that have been conducted mainly in Latin American countries that have evaluated intervention measures for control of cysticercosis including the development and testing of vaccines. Furthermore, the involvement of international agencies and institutions, such as the World Health Organization, the Food and Agriculture Organization and the International Livestock Research Institute, as well as the commitment of policymakers, scientists and field workers, are key means for the sustainable control and, hopefully, eradication of T. solium infections.     

Incidence,economic effects,and control of Haemophilus pleuropneumoniae infections in pigs

Summary

This thesis synopsis reports the results of investigations on:

– the incidence of clinical and subclinical H. pleuropneumoniae infections on pig farms in North Brabant;

– the economic loss on fattening farms; the effect of husbandry;

– the possibility of eradicating H. pleuropneumoniae on infected breeding farms on the basis of serological testing;

– the possibility of control on fattening farms by means of vaccination.

The principal findings were as follows:

Clinical and subclinical H. pleuropneumoniae infections are widespread on pig farms in North Brabant:

The greatest economic loss was due to mortality and veterinary fees; the daily weight again was not found to be affected.

The effect of husbandry.

Less mortality occurred: on farms where the animals were not shifted during the fattening period; in compartments where the all‐in all‐out method was systematically used; in compartments with thermostatically controlled warming of the incoming air; in compartments meeting all standards of a good housing climate.

Various sanitation measures on infected breeding farms were not successful.

Only one experimental vaccine afforded good protection, but because of a high percentage of injection abscesses this vaccine was unsuitable for use in practice.     

Prevalence of Taenia solium porcine cysticercosis in the Eastern, Southern and Western provinces of Zambia

Tongue examination and detection of circulating antigen (Ag-ELISA) were used to establish the prevalence of Taenia solium porcine cysticercosis in free-range pigs in selected districts of Eastern, Southern and Western provinces of Zambia, and to determine if prevalence of porcine cysticercosis was associated with age, breed and sex. Households with pigs were identified using the snowballing technique. A total of 1691 pigs were examined out of which 183 (10.8%) were positive on tongue examination. Ag-ELISA gave a sero-prevalence of 23.3%. When considering the factors in a logistic regression analysis, only breed type was significantly associated with porcine cysticercosis (OR=0.72; 95%CI=0.63-0.81). The crossbred pigs were 72% more likely to have had cysticercosis than the Nsenga (dwarf local) breed as determined by Ag-ELISA. The result that crossbred pigs had a higher prevalence of T. solium cysticercosis suggests that pig breeds may display different susceptibility to cysticercosis. The limited use of latrines in these areas implies that people use the nearby bush for defecation, resulting in pigs having access to human faeces. Therefore, investigation of taeniosis and cysticercosis in humans is warranted to better comprehend the local epidemiology and transmission risks. This should then be followed by extension programs to communities so that the control plans that could be instituted are more sustainable.     

Trichinella pseudospiralis in pig from Croatia

Trichinella spiralis and Trichinella britovi are species that are frequently found in domestic pigs and various sylvatic animals in Croatia. During routine trichinoscopy, non-encapsulated larvae were detected in the muscle tissue of a domestic pig. Artificial digestion revealed a larvae burden of 602 muscle larvae per gram of tissue. Tissue section analysis confirmed the presence of non-encapsulated larvae. Multiplex PCR identified the larvae as T. pseudospiralis. This observation is consistent with the reports of a local veterinary inspector who described the presence of non-encapsulated Trichinella in four individual cases over the last 2 years. This is the first report of T. pseudospiralis in Croatia and one of very few cases of T. pseudospiralis infection described in domestic pigs. The detection of non-encapsulated larvae stresses the need for implementation of artificial digestion instead of trichinoscopy for the detection and identification of Trichinella infections.     

Successful immunization of naturally reared pigs against porcine cysticercosis with a recombinant oncosphere antigen vaccine

Taenia solium causes cysticercosis in pigs and taeniasis and neurocysticercosis in humans. Oncosphere antigens have proven to be effective as vaccines to protect pigs against an experimental infection with T. solium. A pair-matched vaccination trial field, using a combination of two recombinant antigens, TSOL16 and TSOL18, was undertaken in rural villages of Peru to evaluate the efficacy of this vaccine under natural conditions. Pairs of pigs (n=137) comprising one vaccinated and one control animal, were allocated to local villagers. Animals received two vaccinations with 200 μg of each of TSOL16 and TSOL18, plus 5mg Quil-A. Necropsies were performed 7 months after the animals were distributed to the farmers. Vaccination reduced 99.7% and 99.9% (p<0.01) the total number of cysts and the number of viable cysts, respectively. Immunization with the TSOL16-TSOL18 vaccines has the potential to control T. solium transmission in areas where the disease is endemic, reducing the source for tapeworm infections in humans.