T. S. Barnes

Challenges for diagnosis and control of cystic hydatid disease

This paper is based on the experience of the authors, with the aim to define the challenges for Echinococcus granulosus (E.g./CE) diagnosis and control for those countries that may now or in the future be contemplating control of hydatid disease. A variety of methods are available for diagnosis in humans but a universal gold standard is lacking. Diagnosis in definitive hosts can avoid necropsy by the use of methods such as coproantigen detection but test performance is variable between populations. A sylvatic cycle adds challenges in some countries and the epidemiology of the parasite in these hosts is poorly understood. Control by solely administering praziquantel to dogs is not effective in developing countries where the disease is endemic. Additional avenues to pursue include the instigation of participatory planning, use of an existing vaccination for intermediate hosts and development of a vaccine and long-acting anthelmitic implants for definitive hosts. Promoting public acceptance of control of the dog population by humane euthanasia and reduced reproduction is also essential.

Risk factors for bovine respiratory disease in Australian feedlot cattle: use of a causal diagram-informed approach to estimate effects of animal mixing and movements before feedlot entry

A nationwide longitudinal study was conducted to investigate risk factors for bovine respiratory disease (BRD) in cattle in Australian feedlots. After induction (processing), cattle were placed in feedlot pens (cohorts) and monitored for occurrence of BRD over the first 50 days on feed. Data from a national cattle movement database were used to derive variables describing mixing of animals with cattle from other farms, numbers of animals in groups before arrival at the feedlot, exposure of animals to saleyards before arrival at the feedlot, and the timing and duration of the animals move to the vicinity of the feedlot. Total and direct effects for each risk factor were estimated using a causal diagram-informed process to determine covariates to include in four-level Bayesian logistic regression models. Mixing, group size and timing of the animals move to the feedlot were important predictors of BRD. Animals not mixed with cattle from other farms prior to 12 days before induction and then exposed to a high level of mixing (≥4 groups of animals mixed) had the highest risk of developing BRD (OR 3.7) compared to animals mixed at least 4 weeks before induction with less than 4 groups forming the cohort. Animals in groups formed at least 13 days before induction comprising 100 or more (OR 0.5) or 50-99 (OR 0.8) were at reduced risk compared to those in groups of less than 50 cattle. Animals moved to the vicinity of the feedlot at least 27 days before induction were at reduced risk (OR 0.4) compared to cattle undergoing short-haul transportation (<6h) to the feedlot within a day of induction, while those experiencing longer transportation durations (6h or more) within a day of induction were at slightly increased risk (OR 1.2). Knowledge of these risk factors could potentially be used to inform management decisions to reduce the risk of BRD in feedlot cattle.

Impact of anthropogenic and natural environmental changes on Echinococcus transmission in Ningxia Hui Autonomous Region, the People’s Republic of China

Echinococcus transmission is known to be affected by various environmental factors, which may be modified by human influence or natural events including global warming. Considerable population growth in the last fifty years in Ningxia Hui Autonomous Region (NHAR), the People’s Republic of China (PRC), has led to dramatic increases in deforestation and modified agricultural practices. In turn, this has resulted in many changes in the habitats for the definitive and intermediate hosts of both Echinococcus granulosus and E. multilocularis, which have increased the risks for transmission of both parasites, affecting echinococcosis prevalence and human disease. Ecological environmental changes due to anthropogenic activities and natural events drive Echinococcus transmission and NHAR provides a notable example illustrating how human activity can impact on a parasitic infection of major public health significance. It is very important to continually monitor these environmental (including climatic) factors that drive the distribution of Echinococcus spp. and their impact on transmission to humans because such information is necessary to formulate reliable future public health policy for echinococcosis control programs and to prevent disease spread.

The landscape epidemiology of echinococcoses

Echinococcoses are parasitic diseases of major public health importance globally. Human infection results in chronic disease with poor prognosis and serious medical, social and economic consequences for vulnerable populations. According to recent estimates, the geographical distribution of Echinococcus spp. infections is expanding and becoming an emerging and re-emerging problem in several regions of the world. Echinococcosis endemicity is geographically heterogeneous and over time it may be affected by global environmental change. Therefore, landscape epidemiology offers a unique opportunity to quantify and predict the ecological risk of infection at multiple spatial and temporal scales. Here, we review the most relevant environmental sources of spatial variation in human echinococcosis risk, and describe the potential applications of landscape epidemiological studies to characterise the current patterns of parasite transmission across natural and human-altered landscapes. We advocate future work promoting the use of this approach as a support tool for decision-making that facilitates the design, implementation and monitoring of spatially targeted interventions to reduce the burden of human echinococcoses in disease-endemic areas.

HEMATOLOGY AND SERUM BIOCHEMISTRY OF THE BRUSH-TAILED ROCK-WALLABY (PETROGALE PENICILLATA)

In Australia the brush-tailed rock-wallaby (Petrogale penicillata) is the subject of a national recovery plan, and several sites have been selected for reintroductions. Condition of wild populations and individual animals can be monitored using hematologic and serum biochemistry analytes, and hematologic variables have been correlated with postrelease survival in other species. Prior to such monitoring, reference values for blood variables are required, but these data have not been available for the brush-tailed rock-wallaby. During four trapping periods from November 2004 to August 2005, 116 blood samples were collected from 44 brush-tailed rock-wallabies in a wild colony in southeast Queensland. Some variables varied with sex, age, method of restraint, lactation demands, and trapping period. After partitioning, when required, reference ranges for hematology and serum biochemistry variables were established. This study provides the most comprehensive serum biochemistry reference range for any macropodid marsupial yet published.

Description of the pig production systems, biosecurity practices and herd health providers in two provinces with high swine density in the Philippines

A cross-sectional study was conducted between October 2011 and March 2012 in two major pig producing provinces in the Philippines. Four hundred and seventy one pig farms slaughtering finisher pigs at government operated abattoirs participated in this study. The objectives of this study were to group: (a) smallholder (S) and commercial (C) production systems into patterns according to their herd health providers (HHPs), and obtain descriptive information about the grouped S and C production systems; and (b) identify key HHPs within each production system using social network analysis. On-farm veterinarians, private consultants, pharmaceutical company representatives, government veterinarians, livestock and agricultural technicians, and agricultural supply stores were found to be actively interacting with pig farmers. Four clusters were identified based on production system and their choice of HHPs. Differences in management and biosecurity practices were found between S and C clusters. Private HHPs provided a service to larger C and some larger S farms, and have little or no interaction with the other HHPs. Government HHPs provided herd health service mainly to S farms and small C farms. Agricultural supply stores were identified as a dominant solitary HHP and provided herd health services to the majority of farmers. Increased knowledge of the routine management and biosecurity practices of S and C farmers and the key HHPs that are likely to be associated with those practices would be of value as this information could be used to inform a risk-based approach to disease surveillance and control.

Comparative Pathology of Pulmonary Hydatid Cysts in Macropods and Sheep

The development and appearance of hydatid cysts of Echinococcus granulosus in experimentally infected tammar wallabies (Macropus eugenii) and sheep during the period 9-17 months post-infection (mpi) were studied. Cysts of unknown age were also examined from mature, naturally infected sheep. The cysts grew more rapidly and became fertile within a shorter period in wallabies compared with sheep. Cysts from the wallabies were larger in absolute size and were larger relative to the size of the lungs. Microscopical examination revealed that wallaby hydatid cysts developed in small bronchioles. Hydatid cysts in the wallabies had a thicker germinal membrane, with more nuclei and a thicker laminated layer (LL), than hydatid cysts of similar age found in sheep. In contrast, the adventitial layer was thicker in the ovine cysts, comprising a hyalinized layer of degenerate collagen and necrotic cellular debris surrounded by a layer of granulation tissue that was largely absent from lesions in the wallabies. Multilocular cysts were present in sheep, but not in wallabies. The greater thickness of the germinal membrane in wallaby cysts suggests greater parasite activity, which may explain the more rapid growth rate in this host, whereas the thicker adventitial layer in sheep cysts may be restrictive to growth while simultaneously protecting the hydatid from the host immune response. These differences in the parasite-host relationship between macropods and sheep may reflect the relatively recent introduction of the parasite into Australia.

Cystic echinococcosis in a wild population of the brush-tailed rock-wallaby ( Petrogale penicillata ), a threatened macropodid

Infection of small macropodids with the larval stage of Echinococcus granulosus can cause fatalities as well as significant pulmonary impairment and other adverse sequelae. The brush-tailed rock-wallaby (Petrogale penicillata) is a small macropodid listed as vulnerable on the IUCNs Red List of Threatened Species. This study used radiographic techniques to determine the prevalence and severity of pulmonary hydatid infection and growth rates of hydatid cysts in a wild population of this macropodid. The overall prevalence was 15.3% (9/59 animals) with 20.0% (8/40 animals) of adults infected. During the study period, the death of at least 1 infected animal was directly attributed to pulmonary hydatidosis. Rapid cyst growth occurred in some animals (up to 43% increase in cyst volume in 3 months). Cyst volume reduced lung capacity by up to 17%. Secondary pulmonary changes were uncommon but, in 1 animal, resulted in reduction in lung capacity by approximately 50%. Infection was associated with a higher blood urea concentration, but no significant differences in other blood variables were detected. These results indicate that hydatid infection may be a significant risk to threatened populations of small macropodids and should be addressed in conservation management plans for these animals.

Is Mycoplasma bovis a missing component of the bovine respiratory disease complex in Australia

BACKGROUND Bovine respiratory disease complex (BRDC) is a multi-factorial disease in which numerous factors, such as animal management, pathogen exposure and environmental conditions, contribute to the development of acute respiratory illness in feedlot cattle. The role of specific pathogens in the development of BRDC has been difficult to define because of the complex nature of the disease and the presence of implicated bacterial pathogens in the upper respiratory tract of healthy animals. Mycoplasma bovis is an important pathogen of cattle and recognised as a major contributor to cases of mastitis, caseonecrotic bronchopneumonia, arthritis and otitis media. To date, the role of M. bovis in the development of BRDC of Australian feeder cattle has not been investigated. METHODS In this review, the current literature pertaining to the role of M. bovis in BRDC is evaluated. In addition, preliminary data are presented that identify M. bovis as a potential contributor to BRDC in Australian feedlots, which has not been considered previously. RESULTS AND CONCLUSION The preliminary results demonstrate detection of M. bovis in samples from all feedlots studied. When considered in the context of the reviewed literature, they support the inclusion of M. bovis on the list of pathogens to be considered during investigations into BRDC in Australia.

Determination of Coxiella burnetii seroprevalence in macropods in Australia.

Many animal species, including macropods, have the potential to act as atypical reservoirs of the causative agent of Q fever, Coxiella burnetii. The objective of this study was to determine the seroprevalence of C. burnetii in various macropod species in Australia. Competitive and indirect ELISAs were developed for the testing of macropod sera for antibodies to phase II and I C. burnetii antigens separately. A total of 500 macropod serum samples from selected species sampled in eastern and western coastal states of Australia were screened for the presence of anti-C. burnetii antibodies. An overall seroprevalence of 20.8% (95% CI 20.8-20.9%) was observed with 30.4% (30.2-30.9%) in northern Queensland, 13.0% (12.9-13.1%) in southern Queensland, 7.1% (7.1-8.0%) in western Queensland and 22.8% (22.7-22.9%) in south-western Western Australia. These data indicated that macropods represented a potential reservoir for zoonotic transmission of C. burnetii to domestic animals and the human population.