Thesis (SC. D.)--University of Michigan, 1941. / "Lithoprinted." Bibliography: p. 94-104.

The work presented in this thesis focuses on trichinellosis, a food-borne zoonosis caused by a nematode of the genus Trichinella, in Thailand. The main objectives were to characterise human trichinellosis, determine its endemic foci and characterise factors influencing infection in humans and in the pig, which is an important domestic animal reservoir host of Trichinella. The investigations comprised (i) a retrospective review to characterise human trichinellosis in Thailand, (ii) a survey to characterise factors influencing trichinellosis in pigs and (iii) quantitative and qualitative studies to characterise the factors influencing trichinellosis in humans. An analysis of Thai national trichinellosis surveillance data between 1981 and 2008 highlighted the five northernmost provinces in the Northern Region as particularly affected with trichinellosis. The incidence of human trichinellosis in Thailand decreased significantly during this period. Until recently, trichinellosis was found to cluster significantly in these provinces. Domestic pigs and wild boar appeared to be the major sources of infection. Field studies focused on populations in Nan Province in the Northern Region, where specific foci of human trichinellosis have been observed. A survey of pig production in both lowland and highland areas in five districts of Nan Province found small-scale pig production to be predominant. Production and management practices differed significantly between lowland and highland areas. In the highland areas, pig production was mainly for the owners’ own use. The holdings were poorly managed compared with those in lowland areas. A survey of trichinellosis seroprevalence in these five districts showed the disease to be associated with scavenging pigs (OR = 2.96, p = 0.02) and older pigs (OR = 1.02, p = 0.02). Seroprevalence was estimated with 95% confidence and was in the range 0 - 0.36% in lowland areas and 0.46 - 1.48% in highland areas. A pig acquired from a Thai-Laotian border market was among the sero-positive pigs identified in the survey. A survey for trichinellosis in wild animals (n = 97), mostly wild boar (n = 53; 55%), using the digestion method did not detect Trichinella in any of the animals screened. A retrospective gender-matched and age-matched case-control study in four trichinellosis-affected communities during 2003 – 2006 showed that consumption of raw wild boar (OR = 2.66, p = 0.005) and consumption of raw meat at social gatherings (OR = 3.89, p = 0.008) were risk factors, and the belief that alcohol can kill the parasite in raw meat (OR = 0.36, p = 0.03) was a protective factor associated with individual trichinellosis cases. Qualitative studies on communities’ knowledge, attitudes and practices relating to trichinellosis in 12 villages indicated that the communities received information about food-borne diseases. However, the practice of raw food consumption continued because of individual taste preferences and the belief that consuming raw food infrequently and in small amounts lessened the risk of eating infected meat. In terms of pig management, although there had been improvements in the practices within Nan Province, with the majority of pigs kept in pens, due to insufficient pig feed and poor survival rates of piglets in inappropriately designed pens, free-range scavenging still occurred. For control of trichinellosis to be improved, the factors identified as influencing its maintenance in the study areas must be communicated to the local administrative organizations and veterinary and public health offices. This will enable them to construct and implement guidelines for good management practices in pig farms in the highland areas. Additionally, there is a need to specify a requirement for Trichinella-free certification of pigs and meat products sold at the border markets. There is also a requirement for the continued education of the general public regarding the safe consumption of adequately-cooked meat.

Se estudiaron aspectos morfológicos, biológicos y de prevención con probióticos en la infestación por Trichinella spiralis. Se determinó además, la concordancia y asociación entre la probabilidad de infestación y la edad, sexo, síntomas, signos clínicos y pruebas de laboratorio de pacientes afecta-dos en un brote de trichinellosis ocurrido en la ciudad de Bahía Blanca, Bs As, Argentina. Las experiencias se llevaron a cabo en la cátedra de Parasitología Clínica del Departamento de Biología, Bioquímica y Farmacia de la Universidad Nacional del Sur. Se determinó la morfología y morfometría de adultos de Trichinella spiralis. Los machos de T. spiralis midieron 1,04 mm 0,04 de largo por 0,040 mm de ancho; las hembras 1,84 mm 0,136 de largo por 0,040 mm de ancho. La cantidad de hembras de T. spiralis recuperadas tanto en el contenido como en la mucosa intestinal de ratónes BALB/c alcanzó un valor máximo, en el día 5 postinfestación. Con referencia al recuento de huevos/larvas por hembra de Trichinella spiralis, el mayor recuento se observó entre el día 5 y 6 postinfes-tación. La fecundidad media fue 147 Huevos/hembra. La Efectividad Potencial de la infestación experimental fue 55,6% 4,6. Se determinó el efecto de la temperatura sobre la viabilidad de larvas libres y enquistadas de Trichinella spiralis mediante los parámetros clásicos: típica postura de coma, ausencia de movimientos de enrollamiento-desenrollamiento y validando la coloración de Azul de Metileno como alternativa útil y sencilla para determinar viabilidad. La viabilidad de las larvas libres/ enquistadas expresada en días fue de: a 30C 62 / 95 días; a 20C150 / 176 días; a 4C 270/ 325días; a 20C 456/ 589días y la destrucción del 100% de las larvas por calor fue de 80C/100C respectivamente. Tanto las larvas libres como enquistadas de la cepa utilizada permanecieron vivas cuando fueron sometidas a temperaturas aún más rigu-rosas (tanto de congelamiento como calentamiento) que las recomendadas por los Organismos Internacionales para el control de Trichinellosis. Ratones control y ratones alimenta-dos oralmente con los probióticos Lactobacillus casei cepa ATCC 7469 y leche fermentada obtenida por actividad de los gránulos de Kefir, fueron infestados con larvas viables e infec-tivas de Trichinella spiralis. El ciclo evolutivo del parásito se pudo obstaculizar mediante la administración cíclica y conti-nua de los probióticos ya que ambos redujeron la entrada de hembras a la mucosa intestinal, la diseminación de las larvas al torrente circulatorio del hospedador y la posterior invasión de las fibras musculares. Se estudió en pacientes expuestos a T. spiralis durante un brote, la asociación entre infestación, parámetros de laboratorio, y signos clínicos durante la etapa aguda de la enfermedad. Se determinó la concordancia (K) entre las pruebas inmunoserológicas más utilizadas para el diagnóstico de Trichinellosis humana. Durante la primera semana de exposición la fiebre, el edema bipalpebral, la mial-gia acompañados de un aumento de la enzima creatinin-fosfoquinasa y de eosinofilia, se asoció signifi-cativamente con la positividad de los test inmuno-serológicos ELISA, IFI y WB a los 30-35 dias post-infestación, encontrán-dose una concordancia (K) perfecta entre los mismos. / We studied morphological, biological caracteristics and probiotics in preventing infestation by Trichinella spiralis. It also determined the correlation and association between the likelihood of infestation and the age, sex, symptoms and clinical signs and laboratory tests of patients in an outbreak of trichinellosis occurred in the city of Bahia Blanca, Buenos Aires, Argentina. The experiments were carried out in the chair of Clinical Parasitology, Department of Biology, Bioche-mistry and Pharmacy, National University of the South. We determined the morphology and morphometry of adult Trichi-nella spiralis. The males of T. spiralis measured 1,04 mm 0,04 long by 0,040 mm wide, the females 1.84 0.136 mm long by 0,040 mm wide. The number of females of T. spiralis recovered both in content and in the intestinal mucosa of BALB/c mice peaked on day 5 infestation. With reference to count eggs / larvae per female of Trichinella spiralis, the highest was observed between days 5 and 6 after infestation. Average fecundity was 147 eggs / female. Potential Effec-tiveness of experimental infestation was 55.6% 4.6. We determined the effect of temperature on the viability of encysted and larvae free of Trichinella spiralis from classical parameters: typical posture of coma, absence of movements and validating the Methylene Blue staining as a useful and simple alternative to determine viability. The viability of larvae free / encysted in days was: at -30 C 62/95 days at -20 C150 / 176 days at 4 C 270 /325días; at 20 C 456 / 589 days and the destruction of 100% heat of the larvae was 80 C/100 C respectively. Both free larvae and encysted larvae of the strain used remained alive when they were subjected to even more stringent temperatures (both freezing and heating) than those recommended by International Organizations to Control Trichinellosis. Control mice and mice fed with oral probiotic Lactobacillus casei ATCC 7469 strain and fermented milk obtained by the activity of Kefir grains were infected with viable and infective larvae of Trichinella spiralis. The cycle of the parasite was hampered by the continuous and cyclical administration of probiotics since it significantly decreased the entry of the female in the intesti-nal mucosa, preventing the spread of the larvae in the bloods-tream of the host and the subsequent invasion of the fibers muscle. Was studied in patients exposed to T. spiralis during an outbreak, the association between infestation, laboratory parameters and clinical signs during the acute stage of the disease. We determined the concordance (K) between immu-noserological tests commonly used for diagnosis of human Trichinellosis. During the first week of exposure fever, bipal-pebral edema, myalgia accompanied by an increase of the enzyme creatinphosphoquinase and eosinophilia, was signifi-cantly associated with test positivity immunoserological ELISA, IFI and WB at 30-35 days post-infestation, finding a match (K) there between perfect.

Ph.d.-afhandling. University of Helsinki, 2005. / Også elektronisk adgang via Internetttet.

Ph.d.-afhandling. University of Helsinki, 2006. / Også elektronisk adgang via Internettet.

Animal health surveillance is an important part of animal health care, particularly in countries dependent on livestock for food production and international trade. There are two major issues related to the provision of e®ective surveillance activities. Firstly, for good information to become available, the design and conduct of data collection activ- ities should be carried out following sound statistical principles. In reality, constraints such as imperfect tests and unavoidably-biased sampling strategies hinder straightfor- ward analysis and interpretation of survey results. Risk-based surveillance is used to target high-risk sub-populations to increase e±ciency of disease detection; however, biased datasets are generated. This thesis develops methodologies to design risk-based surveillance systems and al- low statistically valid analysis of the inherently biased data they generate. The ¯rst example describes the development of a method to analyse surveillance data gathered for bovine spongiform encephalopathy (BSE). The data are collected from four dif- ferent surveillance streams of animals tested for BSE, with each stream containing unavoidable biases and limitations. In the BSurvE model, these data are combined with demographic information for each birth cohort to estimate the proportion of each birth cohort infected with BSE. The prevalence of BSE in a national herd can then be estimated using the method of moments, whereby the observed number of infected animals is equated with the expected number. The upper 95% con¯dence limit for the prevalence is estimated both for infected countries and for those where no BSE has previously been detected. A similar approach to that used in BSurvE is then applied to surveillance data for trichinellosis, for which risk-based post-mortem testing is also performed. Negative results from multiple species using di®erent, imperfect tests are combined to give an estimate of the upper 95% con¯dence limit of the national prevalence of trichinellosis in a reference population. This method is used to provide support for freedom from trichinellosis in Great Britain. A di®erent approach to risk-based surveillance is explored as the surveillance strategy for detection of exotic causes of abortion in sheep and goats in New Zealand is examined. Using a geographic information system (GIS) maps of disease risk factors were overlain to produce a risk landscape for the lower North Island. This was used to demonstrate how areas of high- and low-risk of disease occurrence can be identi¯ed and used to guide the design of a risk-based surveillance programme. Secondly, within one surveillance objective there may be many ways in which the available funds or human resources could be distributed. This thesis develops a method to assess BSE surveillance programmes, and provides tools to facilitate BSE detection on the basis of infection risk and to increase the e±ciency of surveillance strategies. A novel approach to allocation of resources is developed, where portfolio theory con- cepts from ¯nance are applied to animal health surveillance. The example of surveil- lance for exotic causes of sheep and goat abortion is expanded upon. Risk of disease occurrence is assessed for a population over di®erent time periods and geographical areas within a country, and portfolio theory used to allocate the number of tests to be carried out within each of these boundaries. This method is shown to be more likely to detect disease in a population when compared to proportional allocation of the available resources. The studies presented here show new approaches that allow better utilisation of imperfect data and more e±cient use of available resources. They allow development of surveillance programmes containing an appropriate balance of scanning and targeted surveillance activities. Application of these methods will enhance the implementation and value of surveillance in animal health.

Animal health surveillance is an important part of animal health care, particularly in countries dependent on livestock for food production and international trade. There are two major issues related to the provision of e®ective surveillance activities. Firstly, for good information to become available, the design and conduct of data collection activ- ities should be carried out following sound statistical principles. In reality, constraints such as imperfect tests and unavoidably-biased sampling strategies hinder straightfor- ward analysis and interpretation of survey results. Risk-based surveillance is used to target high-risk sub-populations to increase e±ciency of disease detection; however, biased datasets are generated. This thesis develops methodologies to design risk-based surveillance systems and al- low statistically valid analysis of the inherently biased data they generate. The ¯rst example describes the development of a method to analyse surveillance data gathered for bovine spongiform encephalopathy (BSE). The data are collected from four dif- ferent surveillance streams of animals tested for BSE, with each stream containing unavoidable biases and limitations. In the BSurvE model, these data are combined with demographic information for each birth cohort to estimate the proportion of each birth cohort infected with BSE. The prevalence of BSE in a national herd can then be estimated using the method of moments, whereby the observed number of infected animals is equated with the expected number. The upper 95% con¯dence limit for the prevalence is estimated both for infected countries and for those where no BSE has previously been detected. A similar approach to that used in BSurvE is then applied to surveillance data for trichinellosis, for which risk-based post-mortem testing is also performed. Negative results from multiple species using di®erent, imperfect tests are combined to give an estimate of the upper 95% con¯dence limit of the national prevalence of trichinellosis in a reference population. This method is used to provide support for freedom from trichinellosis in Great Britain. A di®erent approach to risk-based surveillance is explored as the surveillance strategy for detection of exotic causes of abortion in sheep and goats in New Zealand is examined. Using a geographic information system (GIS) maps of disease risk factors were overlain to produce a risk landscape for the lower North Island. This was used to demonstrate how areas of high- and low-risk of disease occurrence can be identi¯ed and used to guide the design of a risk-based surveillance programme. Secondly, within one surveillance objective there may be many ways in which the available funds or human resources could be distributed. This thesis develops a method to assess BSE surveillance programmes, and provides tools to facilitate BSE detection on the basis of infection risk and to increase the e±ciency of surveillance strategies. A novel approach to allocation of resources is developed, where portfolio theory con- cepts from ¯nance are applied to animal health surveillance. The example of surveil- lance for exotic causes of sheep and goat abortion is expanded upon. Risk of disease occurrence is assessed for a population over di®erent time periods and geographical areas within a country, and portfolio theory used to allocate the number of tests to be carried out within each of these boundaries. This method is shown to be more likely to detect disease in a population when compared to proportional allocation of the available resources. The studies presented here show new approaches that allow better utilisation of imperfect data and more e±cient use of available resources. They allow development of surveillance programmes containing an appropriate balance of scanning and targeted surveillance activities. Application of these methods will enhance the implementation and value of surveillance in animal health.

Animal health surveillance is an important part of animal health care, particularly in countries dependent on livestock for food production and international trade. There are two major issues related to the provision of e®ective surveillance activities. Firstly, for good information to become available, the design and conduct of data collection activ- ities should be carried out following sound statistical principles. In reality, constraints such as imperfect tests and unavoidably-biased sampling strategies hinder straightfor- ward analysis and interpretation of survey results. Risk-based surveillance is used to target high-risk sub-populations to increase e±ciency of disease detection; however, biased datasets are generated. This thesis develops methodologies to design risk-based surveillance systems and al- low statistically valid analysis of the inherently biased data they generate. The ¯rst example describes the development of a method to analyse surveillance data gathered for bovine spongiform encephalopathy (BSE). The data are collected from four dif- ferent surveillance streams of animals tested for BSE, with each stream containing unavoidable biases and limitations. In the BSurvE model, these data are combined with demographic information for each birth cohort to estimate the proportion of each birth cohort infected with BSE. The prevalence of BSE in a national herd can then be estimated using the method of moments, whereby the observed number of infected animals is equated with the expected number. The upper 95% con¯dence limit for the prevalence is estimated both for infected countries and for those where no BSE has previously been detected. A similar approach to that used in BSurvE is then applied to surveillance data for trichinellosis, for which risk-based post-mortem testing is also performed. Negative results from multiple species using di®erent, imperfect tests are combined to give an estimate of the upper 95% con¯dence limit of the national prevalence of trichinellosis in a reference population. This method is used to provide support for freedom from trichinellosis in Great Britain. A di®erent approach to risk-based surveillance is explored as the surveillance strategy for detection of exotic causes of abortion in sheep and goats in New Zealand is examined. Using a geographic information system (GIS) maps of disease risk factors were overlain to produce a risk landscape for the lower North Island. This was used to demonstrate how areas of high- and low-risk of disease occurrence can be identi¯ed and used to guide the design of a risk-based surveillance programme. Secondly, within one surveillance objective there may be many ways in which the available funds or human resources could be distributed. This thesis develops a method to assess BSE surveillance programmes, and provides tools to facilitate BSE detection on the basis of infection risk and to increase the e±ciency of surveillance strategies. A novel approach to allocation of resources is developed, where portfolio theory con- cepts from ¯nance are applied to animal health surveillance. The example of surveil- lance for exotic causes of sheep and goat abortion is expanded upon. Risk of disease occurrence is assessed for a population over di®erent time periods and geographical areas within a country, and portfolio theory used to allocate the number of tests to be carried out within each of these boundaries. This method is shown to be more likely to detect disease in a population when compared to proportional allocation of the available resources. The studies presented here show new approaches that allow better utilisation of imperfect data and more e±cient use of available resources. They allow development of surveillance programmes containing an appropriate balance of scanning and targeted surveillance activities. Application of these methods will enhance the implementation and value of surveillance in animal health.