Exposure to Ascaris lumbricoides infection and risk of childhood asthma in north of Iran.

BACKGROUND: Asthma and Ascaris lumbricoides infection are common health issues affecting 250 and 700 million people worldwide, respectively. The relationship between ascariasis and asthma is a matter of substantial interest and research. METHODS: We performed a case-control study to evaluate whether the exposure to Ascaris infection is associated with asthma in children. We also assessed potential risk factors for Ascaris infection and asthma in study area. We enrolled 145 asthmatic children and 115 healthy controls. The Global Initiative for Asthma guideline was used to evaluate asthma symptoms and severity in study participants. Ascaris infection was assessed by the presence of anti-Ascaris IgG ≥ 11 IU/mL measured by enzyme-linked immunosorbent assay. RESULTS: We have found a significant relationship between exposure to Ascaris and asthma (odds ratio, 2.92; 95% CI 1.04-8.18; P value = 0.034), and this relationship remained significant after adjustment for covariates (adjusted OR, 3.36; 95% CI 1.04-13%; P value = 0.047). Ascaris infection was more frequent in children with mild sustainable asthma (13.2%; 15/113) than in children with moderate sustainable asthma (6.2%, 2/32), although there was a non-significant difference between these groups (OR, 2.3; 95% CI 0.5-10.1; P value = 0.35). Based on results of a multi-regression analysis, contact with soil (OR, 6.7; 95% CI 1.9-23.5), and drinking unsafe water (OR, 4.2; 95% CI 1.2-14.2) were significant risk factors for Ascaris infection in the study area. CONCLUSION: Results of this study suggest that A. lumbricoides infection might affect susceptibility to asthma in children. These results could be useful in prevention, early diagnosis and management of childhood asthma.

Meat sources of infection for outbreaks of human trichinellosis.

Trichinellosis is one of the most important foodborne zoonotic diseases, with worldwide distribution. While human risk for trichinellosis has historically been linked to pork, modern pork production systems and slaughter inspection programs have reduced or eliminated pork as a source for trichinellosis in many countries. While pork may no longer pose a significant risk for trichinellosis, many other animal species may be hosts for Trichinella species nematodes and when human consume meat from these animal species, there may be risk for acquiring trichinellosis. This review article describes the various non-pork meat sources of human trichinellosis outbreaks, where these outbreaks have occurred and some of the factors that contribute to human risk. The literature reviewed here provides evidence of the persistence of Trichinella as a human health risk for people who eat meat from feral and wild carnivores and scavengers, as well as some herbivores that have been shown to harbor Trichinella larvae. It points to the importance of education of hunters and consumers of these meats and meat products.

Development of Dose-Response Models to Predict the Relationship for Human Toxoplasma gondii Infection Associated with Meat Consumption.

Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of deaths attributed to foodborne pathogens in the United States. It is thought that a substantial portion of human T. gondii infections is acquired through the consumption of meats. The dose-response relationship for human exposures to T. gondii-infected meat is unknown because no human data are available. The goal of this study was to develop and validate dose-response models based on animal studies, and to compute scaling factors so that animal-derived models can predict T. gondii infection in humans. Relevant studies in literature were collected and appropriate studies were selected based on animal species, stage, genotype of T. gondii, and route of infection. Data were pooled and fitted to four sigmoidal-shaped mathematical models, and model parameters were estimated using maximum likelihood estimation. Data from a mouse study were selected to develop the dose-response relationship. Exponential and beta-Poisson models, which predicted similar responses, were selected as reasonable dose-response models based on their simplicity, biological plausibility, and goodness fit. A confidence interval of the parameter was determined by constructing 10,000 bootstrap samples. Scaling factors were computed by matching the predicted infection cases with the epidemiological data. Mouse-derived models were validated against data for the dose-infection relationship in rats. A human dose-response model was developed as P (d) = 1-exp (-0.0015 × 0.005 × d) or P (d) = 1-(1 + d × 0.003 / 582.414)(-1.479) . Both models predict the human response after consuming T. gondii-infected meats, and provide an enhanced risk characterization in a quantitative microbial risk assessment model for this pathogen.

A Systematic Meta-Analysis of Toxoplasma gondii Prevalence in Food Animals in the United States.

Toxoplasma gondii is a widely distributed protozoan parasite. The Centers for Disease Control and Prevention reported that T. gondii is one of three pathogens (along with Salmonella and Listeria), that together account for >70% of all deaths due to foodborne illness in the United States. Food animals are reservoirs for T. gondii and act as one of the sources for parasite transmission to humans. Based on limited population-based data, the Food and Agriculture Organization/World Health Organization estimated that approximately 22% of human T. gondii infections are meatborne. The objective of the current study was to conduct a systematic meta-analysis to provide a precise estimation of T. gondii infection prevalence in food animals produced in the United States. Four databases were searched to collect eligible studies. Prevalence was estimated in six animal categories (confinement-raised market pigs, confinement-raised sows, non-confinement-raised pigs, lamb, goats, and non-confinement-raised chickens) by a quality-effects model. A wide variation in prevalence was observed in each animal category. Animals raised outdoors or that have outdoor access had a higher prevalence as compared with animals raised indoors. T. gondii prevalence in non-confinement-raised pigs ranked the highest (31.0%) followed by goats (30.7%), non-confinement-raised chickens (24.1%), lambs (22.0%), confinement-raised sows (16.7%), and confinement-raised market pigs (5.6%). These results indicate that T. gondii-infected animals are a food safety concern. The computed prevalence can be used as an important input in quantitative microbial risk assessment models to further predict public health burden.

Over a century of progress on Trichinella research in pigs at the United States Department of Agriculture: Challenges and solutions.

Trichinellosis, caused by 13 species/subspecies/genotypes in the nematode genus Trichinella, is a worldwide zoonosis. In the United States, trichinellosis was of historical and economic significance because of European restrictions on the import of U.S. pork. Before the advent of effective protective measures, most cases of trichinellosis were derived from consumption of undercooked or inadequately processed, infected pork. Research conducted at the United States Department of Agriculture (USDA) since 1891, and policies established by USDA regulatory agencies, have helped to reduce Trichinella infections in commercially raised domestic pigs to negligible levels. Here, we review the history of this scientific progress, placing special emphasis on research conducted at the USDA's Beltsville Agricultural Research Center.

Surveillance for Trichinella infection in U.S. pigs raised under controlled management documents negligible risk for public health.

Biosecurity measures preventing exposure of pigs to rodents, wildlife, and contaminated feed or waste products reduce the risk of zoonotic Trichinella infection in pork. To understand the benefits of such measures in the United States, we conducted the first comprehensive survey of pigs produced under the Pork Quality Assurance Plus production standard, surveying 3,208,643 pork samples from twelve processing locations tested over a period of 54 months. We detected no Trichinella sp. positives in any of these pork samples, providing a 95% confidence in a Trichinella sp. prevalence of <1 in 1,000,000 for the processors represented by the study. These results are consistent with international guidelines for having a negligible risk to public health. Results obtained here should generalize to all PQA+ sources, as Trichinella sp. exposure risk is based on production guidelines that extend to the larger PQA+ population.

Trichinella spp. control in modern pork production systems.

Infection with Trichinella spp. from pork and other sources has been a major public health concern in many parts of the world. This review describes the progression of processes followed to protect consumers from exposure to this parasite. Testing programs for pigs, as required by some countries, have been important in reducing the risk of exposure from commercial pork products. However, improvements in pork production systems in the past several decades, including high levels of bio-security in confinement production systems, have also contributed to major reductions in the occurrence of this parasite in pigs and pork products. International guidelines and regulations have codified requirement for controlled management or controlled housing that prevents risk of exposure of pigs to Trichinella spp. Adhering to these requirements, with appropriate documentation, eliminates the need for individual carcass testing for domestic consumers as well as for purposes of trade. Pigs not produced in controlled housing systems should be subject to testing to confirm absence of Trichinella spp. infection.

The global and regional prevalence, burden, and risk factors for methicillin-resistant Staphylococcus aureus colonization in HIV-infected people: A systematic review and meta-analysis.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is among the most important opportunistic pathogens in HIV+ patients, resulting in considerable morbidity and mortality. METHODS: The MEDLINE, Scopus, Web of Science, and EMBASE databases were comprehensively searched for studies that investigated the prevalence of MRSA colonization in HIV+ patients. We used a random effects model to calculate pooled prevalence estimates with 95% confidence intervals (CI) and analyzed data based on World Health Organization regions. RESULTS: Among 9,772 records identified, 69 were included in the meta-analysis, comprising 30,050 HIV+ patients from 21 countries. We estimated the pooled worldwide prevalence of MRSA in people living with HIV to be 7% (95% CI 5%-9%, 1,623/30,050), with the highest prevalence in Southeast Asia (16%, 95% CI 9%-24%) and the region of the Americas (10%; 95% CI 7%-13%) and lowest prevalence in the European region (1%; 95% CI 0%-1%). Globally, we estimated approximately 2,659,000 (95% CI 1,835,000-3,303,000) HIV+ patients with colonized MRSA. Potential risk factors for MRSA colonization in HIV+ patients included previous MRSA infection (OR, 7.5; 95% CI, 3.91-14.37), hospitalization in the past year (OR, 1.87; 95% CI 1.11-3.16), and use of antibiotics (OR, 2.52; 95% CI 1.39-4.58). CONCLUSIONS: Our findings emphasize the importance of routine screening for MRSA among all HIV+ patients throughout the world, especially in regions that have a high burden of disease.

Treatment of resistant visceral leishmaniasis with interferon gamma in combination with liposomal amphotericin B and allopurinol.

This report describes the first case of visceral leishmaniasis (VL) resistant to pentavalent antimonials and also the first use of combinational therapy in Iran. The patient was a two-year old boy, from a non-endemic area for leishmaniasis in northern Iran, presenting with pentavalent antimonial resistant VL. Additional treatment with conventional and liposomal amphotericin B was not effective. A complete cure was achieved following a three week treatment with liposomal amphotericin B (5 mg/kg/day for 5 days, then on the 14th and 21st days), allopurinol (25 mg/day for 5 days, then on the 14th and 21st days) and interferon gamma (50 µg/m2 subcutaneously three times weekly). Our results suggest a need for further studies to identify resistant Leishmania species and their susceptibility to different treatment regimens.

International Commission on Trichinellosis: Recommendations on post-harvest control of Trichinella in food animals.

Domestic and wild animals which consume meat are at risk of becoming infected with Trichinella and therefore may pose a public health risk. Among domestic livestock, pigs are most commonly associated with Trichinella infection, but human outbreaks have also resulted from consumption of horsemeat, wild boar, bear, walrus and other wild animals. For animals that are not produced under controlled management conditions and for wild animals, specific steps should be taken to prevent human exposure to Trichinella. These steps include appropriate testing of individual carcasses to identify those that pose a public health risk, post-slaughter processing to inactivate Trichinella in meat that might be infected, and education of consumers regarding the need for proper preparation methods for meat that might contain Trichinella larvae. The International Commission on Trichinellosis recognizes three (3) acceptable means of treatment to render potentially Trichinella-infected meats safe for consumption: 1) cooking, 2) freezing (for meat from domestic pigs), and 3) irradiation. Proper use of these methods is described here, along with specific cautions on use of other methods, including curing and heating with microwaves.

International Commission on Trichinellosis: Recommendations on pre-harvest control of Trichinella in food animals.

Transmission of Trichinella to domestic livestock, notably pigs, is limited to certain risk factors including feeding of raw meat-containing waste products or animal carcasses and exposure to infected rodents and wildlife. Prevention of infection in food animals is dependent on eliminating risk of exposure to these potential sources of Trichinella. By implementing conditions of controlled management, pig herds can be considered to pose a negligible risk for Trichinella, and groups of herds which follow these same conditions can be considered to be a compartment with negligible risk for Trichinella. Pork from pigs originating from a negligible risk herd or compartment would not require further testing or processing to protect consumers from this parasite. Verifying the status of pigs from a controlled management negligible risk herd or compartment can be accomplished by a program of regular audits or by implementing surveillance testing of a statistical sample of pigs from the herd or compartment.

International Commission on Trichinellosis: Recommendations for quality assurance in digestion testing programs for Trichinella.

Effective performance of digestion testing methods for Trichinella, and their use for the detection of infected animals and the prevention of human trichinellosis require system-wide incorporation of appropriate quality assurance (QA) practices. The recommendations of the International Commission on Trichinellosis (ICT) aim to facilitate reliable test results when laboratories operate within a quality management system (QMS) which includes: 1) a quality manual (or similar documentation of the QMS); 2) a validated test method with identified critical control points; 3) a training program; 4) procedures utilizing proficiency testing and other methods to confirm technical capability of analysts; 5) equipment calibration and maintenance; 6) standard operating procedures, related documentation and reporting; 7) procedures to enable continuous monitoring and improvements; and 8) regular internal and third party audits. The quality manual or similar documentation describes the QMS within a testing laboratory, and lists the QA policies and good laboratory practices. Quality assurance goals contained in such documentation are the foundation of an effective QA program and must be explicit, measurable, and expressed in terms of performance criteria for the test method based on purpose for testing. The digestion method is capable of consistently detecting Trichinella larvae in meat at a level of sensitivity that is recognized to be effective for use in controlling animal infection and preventing human disease. However, consistent performance of the assay is assured only when parameters of the test method have been defined, scientifically validated as fit for purpose, and used within an effective QMS. The essential components of a digestion assay, specifically the critical control points and minimum standards for test performance are described. Reliable proficiency samples and their appropriate use in a quality system are key factors for certifying and maintaining an effective testing laboratory, including qualifying, re-qualifying and disqualifying of analysts as appropriate. Thus recommendations are included for the preparation and use of proficiency samples in a Trichinella digestion testing laboratory. The minimum training requirements for analysts performing a quality assured digestion assay, as well as suggested requirements for the content of a training manual, are also outlined. Finally, these ICT recommendations include essential components and minimum standards for maintaining and achieving certification and maintenance of a laboratory performing digestion testing for Trichinella. The certification program for the laboratory, including qualifying analysts, may be administered by a National Reference Laboratory or an authorized third party certifying body, under the auspices of the appropriate competent authority.

The global seroprevalence of Toxoplasma gondii in pigs: A systematic review and meta-analysis.

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is an important disease with worldwide distribution. Infection can occur from ingesting raw or undercooked infected meat, and among food animal species, pork is known to be one of the main sources of meat-borne infection. Here, we present results of the first systematic review and meta-analysis on the global T. gondii seroprevalence in pigs. PubMed/MEDLINE, Scopus, and EMBASE databases were comprehensively searched for relevant studies published between January 1, 1990 and October 25, 2018. We used a random effects model to calculate pooled seroprevalence estimates with 95% confidence intervals (CI) and analyzed data from five continents. We also conducted subgroup and meta-regression analyses to evaluate the effects of geographical and climate variables on pooled seroprevalence rates. Among 1542 publications identified, 148 studies containing 150 datasets were included in the meta-analysis, and comprised 148,092 pigs from 47 countries. The pooled global T. gondii seroprevalence in pigs was estimated to be 19% (95%CI, 17-22%; 23,696/148,092), with the lowest seroprevalence in Europe (13%; 10-15%) and highest seroprevalence in Africa (25%; 17-34%) and North America (25%; 19-33%). The seropositivity rates in Asia and South America regions were (21%, 16-26%) and (23%; 17-30%), respectively. A significantly higher T. gondii seroprevalence was associated with higher mean annual temperature and lower geographical latitude. The presence of cats on farms was identified as a potential risk factor for T. gondii seropositivity (OR, 1.41; 95%CI, 1.00-2.02). Our findings highlight the importance of pigs as a possible source of human T. gondii infections.

An updated meta-analysis of the association between Toxoplasma gondii infection and risk of epilepsy.

Toxoplasma gondii is a neurotropic pathogen with worldwide distribution. To evaluate the association between Toxoplasma infection and the risk of epilepsy by meta-analysis, observational peer-reviewed studies were retrieved from PubMed, Embase, Web of Science, Scopus and Google Scholar (up to 10 October 2018) and by reference review. Pooled risk estimates were calculated using a random effects model. Heterogeneity was assessed using Cochrane's Q-test and I2. In total, 16 eligible studies involving 19 data sets were included for the final analysis. A total 7897 participants (3771 epileptic patients, 4026 healthy controls) were included. The pooled odds ratio (OR) for Toxoplasma infection was increased to 1.72 (95% confidence interval [CI] 1.37 to 2.16) among patients with epilepsy. There was moderate heterogeneity among the studies (χ2=39.8, I2=62.3%, p=0.001). The ORs from subgroup analyses showed that both cryptogenic epilepsy (OR 2.65 [95% CI 1.91 to 3.68]) and active convulsive epilepsy (OR 1.37 [95% CI 1.09 to 1.72]) were significantly associated with Toxoplasma infection. Another subgroup analyses according to age showed a significant positive association in children (OR 1.33), adults (OR 1.57) and in all ages (OR 1.89). Our findings support the association between Toxoplasma infection and epilepsy. More prospective studies with larger sample sizes and more experimental studies are recommended to elucidate a causative relationship.

Acute Toxoplasma infection in pregnant women worldwide: A systematic review and meta-analysis.

BACKGROUND: Acute Toxoplasma infection (ATI) during pregnancy, if left untreated, can cause severe adverse outcomes for the fetus and newborn. Here, we undertook a meta-analysis to estimate the worldwide prevalence of ATI in pregnant women. METHODS: We searched international databases for studies published between January 1988 and November 2018. We included population-based cross-sectional and prospective cohort studies that reported the prevalence of ATI in pregnant women. Data were synthesized using a random effect model to calculate the overall prevalence of ATI (with a 95% CI) in six WHO regions and globally. We also performed linear meta-regression analyses to investigate associations of maternal, socio-demographic, geographical and climate parameters with the prevalence of ATI. RESULTS: In total, 217 studies comprising 902,228 pregnant women across 74 countries were included in the meta-analysis. The overall prevalence of ATI in pregnant women globally was 1.1% (95% CI: 0.9-1.2%). In studies where more strict criteria for ATI were used, the overall prevalence was 0.6% (95% CI: 0.4-0.7%). The prevalence was highest in the Eastern Mediterranean region (2.5%; 95%CI: 1.7-3.4%) and lowest in the European region (0.5%; 95% CI: 0.4-0.7%). A significantly higher prevalence of ATI was found in countries with lower income levels (P = 0.027), lower human development indices (P = 0.04), higher temperatures (P = 0.02) and lower latitudes (P = 0.005) and longitudes (P = 0.02). CONCLUSIONS: The risk of acquiring ATI during gestation is clinically important and preventive measures to avoid exposure of pregnant women to Toxoplasma infection should be strictly applied.

The global seroprevalence of Toxoplasma gondii among wild boars: A systematic review and meta-analysis.

This systematic review and meta-analysis study was performed to evaluate the worldwide seroprevalence of Toxoplasma gondii among wild boar. We searched PubMed, Science Direct, Web of Science, Cochrane, Scopus, EBSCOhost and Google Scholar databases for studies reporting T. gondii seroprevalence in wild boars between January 1995 and March 2017. Inclusion and exclusion criteria were applied. We estimated the pooled seroprevalence of T. gondii in wild boars using a random-effects model, and evaluated overall seroprevalence in different geographical areas. A total of 43 articles that included 16788 wild boar from 23 countries fulfilled our eligibility criteria. Of these, 4759 wild boar had been defined T. gondii seropositive and we estimated the pooled worldwide seroprevalence of toxoplasmosis in wild boars to be 23% (95% CI: 19-27%). The pooled seroprevalence in North America (32%, 20-45%; odds ratio [OR] 2.09) and Europe (26%, 21-30%; OR 1.72), was higher than Asia (13%, 5-23%). The lowest seroprevalence was estimated in South America (5%, 3-8%). An increased seropositivity was observed with elevation in geographical latitude. In subgroup analyses, the pooled seroprevalence of T. gondii was higher in wild boar older than 12 months of age (28%, 22-35%; OR 1.57) compared to those up to 12 months of age (20%, 16-25%). Our findings suggest that wild boar have an important role in human infection and the epidemiological cycle of T. gondii infection.

Comparison of detection methods for Toxoplasma gondii in naturally and experimentally infected swine.

Results from recent serological surveys and epidemiological studies show that pigs raised in a variety of management systems can be carriers of the tissue cyst stage of Toxoplasma gondi. This parasite can be transmitted to humans through the consumption of improperly prepared pork, making detection and removal of infected swine carcasses from the food chain an important food safety issue. Several methods are available for detection of T. gondii infected swine, including serological assays, polymerase chain reaction, and animal bioassays. The aim of the present study was to compare the detection sensitivities of six of these commonly used methods for detection of T. gondii infection in tissues from naturally and experimentally infected pigs. The results indicate that a serum-based ELISA is the most sensitive method, of those tested, for detection of T. gondii infected swine.

Quantifying the Risk of Human Toxoplasma gondii Infection Due to Consumption of Domestically Produced Lamb in the United States.

UNLABELLED: Toxoplasma gondii is a prevalent protozoan parasite worldwide. Human toxoplasmosis is responsible for considerable morbidity and mortality in the United States, and meat products have been identified as an important source of T. gondii infections in humans. The goal of this study was to develop a farm-to-table quantitative microbial risk assessment model to predict the public health burden in the United States associated with consumption of U.S. domestically produced lamb. T. gondii prevalence in market lambs was pooled from the 2011 National Animal Health Monitoring System survey, and the concentration of the infectious life stage (bradyzoites) was calculated in the developed model. A log-linear regression and an exponential doseresponse model were used to model the reduction of T. gondii during home cooking and to predict the probability of infection, respectively. The mean probability of infection per serving of lamb was estimated to be 1.5 cases per 100,000 servings, corresponding to ∼6,300 new infections per year in the U.S. POPULATION: Based on the sensitivity analysis, we identified cooking as the most effective method to influence human health risk. This study provided a quantitative microbial risk assessment framework for T. gondii infection through consumption of lamb and quantified the infection risk and public health burden associated with lamb consumption.

Trichinae certification in the United States pork industry.

Control of Trichinella infection in U.S. pork has traditionally been accomplished by inspection of individual carcasses at slaughter or by post-slaughter processing to inactivate parasites. We propose that an alternative to individual carcass testing or processing can be used when pigs are raised in production systems where risk of exposure to Trichinella spiralis has been mitigated. Declines in prevalence of this parasite in U.S. domestic swine during the last 30 years, coupled with improvements in pork production systems, now allow Trichinella control to be shifted to the farm through implementation of specific pork production practices. Knowledge of risk factors for exposure of swine to T. spiralis was used to develop an objective audit of risk that can be applied to pork production sites. In a pilot study, 461 production site audits were performed by trained veterinary practitioners. The on-farm audit included aspects of farm management, bio-security, feed and feed storage, rodent control programs and general hygiene. Of the 461 production site audits, 450 audits (97.6%) indicated compliance with the required good production practices. These sites are eligible for certification under the U.S. Trichinae Certification Program and will be audited regularly to maintain that status. The described trichinae certification mechanism will establish a process for ensuring the Trichinella safety of swine, and ultimately food products derived from swine, at the production level.

Qualitative Assessment for Toxoplasma gondii Exposure Risk Associated with Meat Products in the United States.

Toxoplasma gondii is a global protozoan parasite capable of infecting most warm-blooded animals. Although healthy adult humans generally have no symptoms, severe illness does occur in certain groups, including congenitally infected fetuses and newborns, immunocompromised individuals including transplant patients. Epidemiological studies have demonstrated that consumption of raw or undercooked meat products is one of the major sources of infection with T. gondii. The goal of this study was to develop a framework to qualitatively estimate the exposure risk to T. gondii from various meat products consumed in the United States. Risk estimates of various meats were analyzed by a farm-to-retail qualitative assessment that included evaluation of farm, abattoir, storage and transportation, meat processing, packaging, and retail modules. It was found that exposure risks associated with meats from free-range chickens, nonconfinement-raised pigs, goats, and lamb are higher than those from confinement-raised pigs, cattle, and caged chickens. For fresh meat products, risk at the retail level was similar to that at the farm level unless meats had been frozen or moisture enhanced. Our results showed that meat processing, such as salting, freezing, commercial hot air drying, long fermentation times, hot smoking, and cooking, are able to reduce T. gondii levels in meat products. whereas nitrite and/or nitrate, spice, low pH, and cold storage have no effect on the viability of T. gondii tissue cysts. Raw-fermented sausage, cured raw meat, meat that is not hot-air dried, and fresh processed meat were associated with higher exposure risks compared with cooked meat and frozen meat. This study provides a reference for meat management control programs to determine critical control points and serves as the foundation for future quantitative risk assessments.