A Case of Lepromatous Leprosy (Lucio's Phenomenon) Presenting as Periorbital Edema.

Despite low prevalence of leprosy worldwide, new cases continue to present and require swift evaluation and diagnosis to prevent complications. Here, we describe a case of lepromatous leprosy with Lucio's phenomenon initially presenting with facial and periorbital edema. A 38-year-old Brazilian woman presented to the emergency department with facial swelling and erythema, initially treated as cellulitis. Due to rapid worsening despite broad-spectrum antibiotics, she underwent soft tissue exploration and biopsy due to concern for necrotizing fasciitis. During her course, she also developed retiform purpura of bilateral upper and lower extremities. Periorbital and lower extremity pathological specimens ultimately revealed acid-fast bacilli consistent with Mycobacterium leprae , and the patient improved with multidrug therapy. This case illustrates the diagnostic difficulty of lepromatous leprosy with Lucio's phenomenon, which can initially present with periorbital edema.

Endothelial Glycocalyx Morphology in Different Flow Regions of the Aqueous Outflow Pathway of Normal and Laser-Induced Glaucoma Monkey Eyes.

Glycocalyx morphology was examined in the trabecular outflow pathway of monkey eyes with and without experimental glaucoma. Laser burns were administered along ~270 degrees of the trabecular meshwork (TM) of one eye (n = 6) or both eyes (n = 2) of each monkey until intraocular pressure remained elevated. Portions of the TM were not laser-treated. Unlasered eyes (n = 6) served as controls. Enucleated eyes were perfused at 15 mmHg to measure the outflow facility, perfused with fluorescein to evaluate the outflow pattern, perfusion-fixed for glycocalyx labeling, and processed for electron microscopy. Coverage and thickness of the glycocalyx were measured in the TM, Schlemm's canal (SC), collector channels (CCs), intrascleral veins (ISVs), and episcleral veins (ESVs) in non-lasered regions and high- and low-flow regions of controls. Compared to controls, laser-treated eyes had decreased outflow facility (p = 0.02). Glycocalyx thickness increased from the TM to ESVs in non-lasered regions and controls (p < 0.05). Glycocalyx coverage was generally greater distally in non-lasered regions (p < 0.05). In lasered regions, TM, SC, and CCs were partly to completely obliterated, and ISVs and ESVs displayed minimal glycocalyx. Whether the glycocalyx is decreased in the trabecular outflow pathway of human glaucomatous eyes warrants investigation.

Descemet's membrane injury due to bullet shockwave trauma.

Purpose: To report a case of corneal edema associated with Descemet membrane (DM) damage likely due to shockwave trauma from a bullet passing by the eye. Observations: A 27-year-old man presented to the emergency department with pain, redness, and severely decreased vision in the left eye immediately following a gun assault. Examination of the eye revealed a temporal conjunctival laceration, corneal edema, hyphema, and vitreous hemorrhage. Bullets were found in the patient's left chest and axilla, and a laceration was present on the bridge of his nose, but no foreign bodies were found in or around the eyes. The intraocular hemorrhage and corneal edema gradually resolved, and it became apparent that there were DM irregularities that possibly represented micro-ruptures. After 7 months, uncorrected visual acuity improved to 20/25, and the cornea was free of edema but had persistent small focal areas of DM thickening and scarring. Conclusions and Importance: This case illustrates that DM and possibly endothelial cell damage can occur due to shockwave injury from high-speed projectiles. In our case of presumed small central DM micro-ruptures, the corneal edema resolved, and the vision significantly improved with topical therapy and observation, suggesting an overall good prognosis from such injuries.

Schlemm's Canal Endothelium Cellular Connectivity in Giant Vacuole and Pore Formation in Different Flow-type Areas: A Serial Block-Face Scanning Electron Microscopy Study.

Glaucoma is associated with increased resistance in the conventional aqueous humor (AH) outflow pathway of the eye. The majority of resistance is thought to reside in the juxtacanalicular connective tissue (JCT) region of the trabecular meshwork and is modulated by the inner wall (IW) endothelial cells of Schlemm's canal (SC). The IW cells form connections with the underlying JCT cells/matrix, and these connections are thought to modulate outflow resistance. Two ways by which AH crosses the IW endothelium are through: 1) the formation of outpouchings in IW cells called giant vacuoles (GVs) and their intracellular pores (I-pores), and 2) intercellular pores between two adjacent IW cells (B-pores). AH outflow is segmental with areas of high-, low-, and non-flow around the circumference of the eye. To investigate whether changes in cellular connectivity play a role in segmental outflow regulation, we used global imaging, serial block-face scanning electron microscopy (SBF-SEM), and 3D reconstruction to examine individual IW cells from different flow areas of ex vivo perfused normal human donor eyes. Specifically, we investigated the differences in cellular dimensions, connections with JCT cells/matrix, GVs, and pores in SC IW cells between high-, low-, and non-flow areas. Our data showed that: 1) IW cell-JCT cell/matrix connectivity was significantly decreased in the cells in high-flow areas compared to those in low- and non-flow areas; 2) GVs in the cells of high-flow areas had significantly fewer connections beneath them compared to GVs in the cells of low- and non-flow areas; 3) Type IV GVs (with I-pores and basal openings) had significantly fewer connections beneath them compared to Type I GVs (no I-pore or basal opening). Our results suggest that a decreased number of cellular connections between the IW and JCT in high-flow areas is associated with increased numbers of GVs with I-pores and larger Type IV GVs observed in previous studies. Therefore, modulating the number of cellular connections may affect the amount of high-flow area around the eye and thereby modulate AH outflow.

Morphological changes to Schlemm's canal and the distal aqueous outflow pathway in monkey eyes with laser-induced ocular hypertension.

Though roughly 30-50% of aqueous outflow resistance resides distal to Schlemm's canal (SC), the morphology of the conventional outflow pathway distal to SC has not been thoroughly evaluated. This study examined the morphological changes along proximal and distal aspects of the conventional aqueous outflow pathway and their association with decreased outflow facility in an experimental model of glaucoma in cynomolgus macaques. Nd:YAG laser burns were made to 270-340 degrees of the trabecular meshwork (TM) of one eye (n = 6) or both eyes (n = 2) of each monkey to induce ocular hypertension. Distinct regions of the TM were left unlasered. Contralateral eyes (n = 5) were not lasered and were utilized as controls. Monkeys were sacrificed ≥58 months after their last laser treatment. All eyes were enucleated and perfused at 15 mmHg for 30 min to measure outflow facility. Two pairs of eyes were also perfused with fluorescein to examine segmental outflow. All eyes underwent perfusion-fixation for 1 h. Anterior segments were cut into radial wedges and processed for light and electron microscopy. Width, height, and cross-sectional area (CSA) of SC were compared between high- and low-flow regions of control eyes, and between non-lasered regions of laser-treated eyes and control eyes. Number and CSA of intrascleral veins (ISVs) were compared between non-lasered and lasered regions of laser-treated eyes and control eyes, and between high- and low-flow regions of control eyes. Scleral collagen fibril diameter was compared between control eyes and lasered and non-lasered regions of laser-treated eyes. Median outflow facility was significantly decreased in laser-treated eyes compared to control eyes (P = 0.02). Median CSA and height of SC were smaller in high-flow regions than low-flow regions of control eyes (P < 0.05). Median width of SC was not significantly different between high- and low-flow regions of control eyes (P > 0.05). Median CSA, width, and height of SC were not different between non-lasered regions and control eyes (P > 0.05). SC was partially or completely obliterated in lasered regions. Median number of ISVs was significantly decreased in lasered regions compared to non-lasered regions (P < 0.01) and control eyes (P < 0.01). Median CSA of ISVs did not differ between these groups (P > 0.05). Median number and CSA of ISVs were not significantly different between high- and low-flow regions of control eyes (P > 0.05). Lasered regions displayed looser scleral stroma and smaller median diameter of collagen fibrils adjacent to the TM compared to non-lasered regions (P < 0.05) and control eyes (P < 0.05). Dense TM, partial to complete obliteration of SC, and a decreased number of patent ISVs may account in part for the decreased outflow facility in monkey eyes with laser-induced ocular hypertension. The significance of changes in scleral structure in laser-treated eyes warrants further investigation.

Relationships between Intraocular Pressure, Effective Filtration Area, and Morphological Changes in the Trabecular Meshwork of Steroid-Induced Ocular Hypertensive Mouse Eyes.

We investigated whether an inverse relationship exists between intraocular pressure (IOP) and effective filtration area (EFA) in the trabecular meshwork (TM) in a steroid-induced ocular hypertensive (SIOH) mouse model and the morphological changes associated with the reduction of EFA. C57BL/6 mice (n = 15 per group) received either 0.1% dexamethasone (DEX) or saline eye drops twice daily for five weeks. IOP was measured weekly. Fluorescent tracers were injected into the anterior chamber to label EFA at the endpoint. Injected eyes were fixed and processed for confocal microscopy. EFA in the TM was analyzed. Light and electron microscopy were performed in high- and low-tracer regions of six eyes per group. The mean IOP was ~4 mm Hg higher in DEX-treated than saline-treated control eyes (p < 0.001) at the endpoint. EFA was reduced in DEX-treated eyes compared to controls (p < 0.01) and negatively correlated with IOP (R2 = 0.38, p = 0.002). Reduced thickness of juxtacanalicular tissue (JCT) and increased abnormal extracellular matrix in the JCT were found to be associated with reduced EFA. Our data confirm the inverse relationship between EFA and IOP, suggesting that morphological changes in the JCT contribute to the reduction of EFA, thus elevating IOP in SIOH mouse eyes.

Five-year outcomes of selective laser trabeculoplasty: A retrospective study.

Introduction: Studies have shown the efficacy of selective laser trabeculoplasty (SLT) to lower intraocular pressure (IOP) as adjuvant therapy during short-term follow-up. However, few studies have assessed the long-term efficacy of SLT on preventing worsening Humphrey visual field (HVF) parameters and thinning of the retinal nerve fiber layer (RNFL) with continued medical therapy. Methods: A retrospective chart review was conducted of 51 eyes of 39 patients with glaucoma treated with SLT at Boston Medical Center between 2012 and 2016 with 3- and 5-year follow-up. Outcome measures included IOP, visual acuity, number of glaucoma medications, number of months to subsequent surgical intervention. HVF outcome measures included mean deviation (MD) and pattern standard deviation (PSD). Optical coherence tomography (OCT) outcome measures included RNFL mean thickness, and superior and inferior thicknesses. Results: Twenty-five eyes received subsequent surgical intervention (mean time to intervention = 33.6 ± 20.0 months). In the eyes that did not receive another intervention, mean IOP was significantly decreased by 3.2 and 3.5 mmHg at 3- and 5-year after SLT, respectively. Mean number of glaucoma medications was significantly increased at 5-year (2.7 ± 1.6; P = 0.04), compared to pre-SLT (2.0 ± 1.1). Mean HVF MD was significantly higher at 5-year (-7.64 ± 6.57 dB) compared to pre-SLT (-5.61 ± 3.90 dB). Mean PSD significantly increased at 3-year (5.30 ± 2.91 dB) and 5-year (6.84 ± 2.62 dB), compared to pre-SLT (4.63 ± 2.70 dB; P = 0.04 and ≤0.01, respectively). On OCT, inferior quadrant RNFL thickness decreased significantly at 5-year (88.5 ± 19.3 µm), compared to pre-SLT (94.0 ± 23.2 µm). Discussion: Although 51% of eyes had IOP controlled at 5-year post-SLT, mean number of glaucoma medications was significantly higher. Also, there was progression of MD and PSD on HVF and inferior quadrant thinning on OCT at 5-year. We found a significant association between age at SLT and risk of subsequent surgical intervention over 5-year follow-up. Our study adds to our understanding of long-term outcomes of adjuvant SLT for glaucoma patients receiving medical therapy.

Morphological factors associated with giant vacuoles with I-pores in Schlemm's canal endothelial cells of human eyes: A serial block-face scanning electron microscopy study.

Increased intraocular pressure (IOP) is the main risk factor for primary open-angle glaucoma and results from impaired drainage of aqueous humor (AH) through the trabecular outflow pathway. AH must pass the inner wall (IW) endothelium of Schlemm's canal (SC), which is a monolayer held together by tight junctions, to exit the eye. One route across the IW is through giant vacuoles (GVs) with their basal openings and intracellular pores (I-pores). AH drainage through the trabecular outflow pathway is segmental. Whether more GVs with both basal openings and I-pores are present in the active flow areas and factors that may influence formation of GVs with I-pores have not been fully elucidated due to limitations in imaging methods. In this study, we applied a relatively new technique, serial block-face scanning electron microscopy (SBF-SEM), to investigate morphological factors associated with GVs with I-pores in different flow areas. Two normal human donor eyes were perfused at 15 mmHg with fluorescent tracers to label the outflow pattern followed by perfusion-fixation. Six radial wedges of trabecular meshwork including SC (2 each from high-, low-, and non-flow areas) were imaged using SBF-SEM (total: 9802 images). Total GVs, I-pores, basal openings, and four types of GVs were identified. Percentages of GVs with I-pores and basal openings and number of I-pores/GV were determined. Overall, 14.4% (477/3302) of GVs had I-pores. Overall percentage of GVs with both I-pores and basal openings was higher in high- (15.7%), than low- (12.6%) or non-flow (7.3%) areas. Of GVs with I-pores, 83.2% had a single I-pore; 16.8% had multiple I-pores (range: 2-6). Additionally, 180 GVs (90 with I-pores and 90 without I-pores) were randomly selected, manually segmented, and three-dimensionally (3D) reconstructed to determine size, shape, and thickness of the cellular lining. Size of GVs (including median volume, surface area, and maximal cross-sectional area) with I-pores (n = 90) was significantly larger than GVs without I-pores (n = 90) using 3D-reconstructed GVs (P ≤ 0.01). Most I-pores (73.3%; 66/90) were located on or close to GV's maximal cross-sectional area with significant thinning of the cellular lining. Our results suggest that larger size and thinner cellular lining of GVs may contribute to formation of GVs with I-pores. More GVs with I-pores and basal openings were observed in high-flow areas, suggesting these GVs do provide a channel through which AH passes into SC and that increasing this type of GV may be a potential strategy to increase aqueous outflow for glaucoma treatment.

Developing a Simulated Online Model That Integrates GNSS, Accelerometer and Weather Data to Detect Parturition Events in Grazing Sheep: A Machine Learning Approach.

In the current study, a simulated online parturition detection model is developed and reported. Using a machine learning (ML)-based approach, the model incorporates data from Global Navigation Satellite System (GNSS) tracking collars, accelerometer ear tags and local weather data, with the aim of detecting parturition events in pasture-based sheep. The specific objectives were two-fold: (i) determine which sensor systems and features provide the most useful information for lambing detection; (ii) evaluate how these data might be integrated using ML classification to alert to a parturition event as it occurs. Two independent field trials were conducted during the 2017 and 2018 lambing seasons in New Zealand, with the data from each used for ML training and independent validation, respectively. Based on objective (i), four features were identified as exerting the greatest importance for lambing detection: mean distance to peers (MDP), MDP compared to the flock mean (MDP.Mean), closest peer (CP) and posture change (PC). Using these four features, the final ML was able to detect 27% and 55% of lambing events within ±3 h of birth with no prior false positives. If the model sensitivity was manipulated such that earlier false positives were permissible, this detection increased to 91% and 82% depending on the requirement for a single alert, or two consecutive alerts occurring. To identify the potential causes of model failure, the data of three animals were investigated further. Lambing detection appeared to rely on increased social isolation behaviour in addition to increased PC behaviour. The results of the study support the use of integrated sensor data for ML-based detection of parturition events in grazing sheep. This is the first known application of ML classification for the detection of lambing in pasture-based sheep. Application of this knowledge could have significant impacts on the ability to remotely monitor animals in commercial situations, with a logical extension of the information for remote monitoring of animal welfare.

Macular vessel density versus ganglion cell complex thickness for detection of early primary open-angle glaucoma.

BACKGROUND: To evaluate the macular vessel density (VD) and ganglion cell complex (GCC) thickness in pre-perimetric (PPG) and early perimetric primary open-angle glaucoma (PG) eyes, and to compare the diagnostic ability of the two measurements to discriminate PPG and early PG eyes from healthy eyes. METHODS: Seventy-nine eyes in 72 subjects (31 normal, 26 PPG, and 22 early PG eyes) were included in the consecutive case series. Macular VD and GCC thickness were acquired simultaneously using the 6 × 6 mm2 high-density AngioRetina scanning mode. Diagnostic abilities were assessed using the area under the receiver operating characteristic curve (AUROC). RESULTS: Compared to healthy eyes, whole image VD (wiVD) and GCC thickness were significantly lower in PPG and early PG eyes (all P < 0.025). The percent reduction of wiVD was lower than that of GCC thickness in early PG eyes (P < 0.05), while they were similar in PPG eyes (P > 0.05). Regionally, greater VD attenuation and GCC thinning were identified in the perifovea than in the parafovea in both groups (all P < 0.05). Moreover, the percent reduction of VD was less than that of GCC thickness in the perifoveal region in PPG eyes (P < 0.05). The AUROCs for wiVD and GCC thickness were 0.824 and 0.881, respectively, in PPG eyes (P > 0.05), and 0.918 and 0.977, respectively, in early PG eyes (P > 0.05). CONCLUSIONS: Macular VD and GCC thickness significantly decreased in PPG and early PG eyes. The perifoveal region appeared to be more vulnerable to macular VD attenuation and GCC thinning in early glaucoma. Our results showed that macular VD measurements may be helpful for detecting and understanding early glaucomatous damage.

Towards sensor-based calving detection in the rangelands: a systematic review of credible behavioral and physiological indicators.

Calving is a critical point in both a cow and calf's life, when both become more susceptible to disease and risk of death. Ideally, this period is carefully monitored. In extensive grazing systems, however, it is often not economically or physically possible for producers to continuously monitor animals, and thus, calving frequently goes undetected. The development of sensor systems, particularly in these environments, could provide significant benefits to the industry by increasing the quantity and quality of individual animal monitoring. In the time surrounding calving, cows undergo a series of behavioral and physiological changes, which can potentially be detected using sensing technologies. Before developing a sensor-based approach, it is worthwhile considering these behavioral and physiological changes, such that the appropriate technologies can be designed and developed. A systematic literature review was conducted to identify changes in the dam's behavioral and physiological states in response to a calving event. Articles (n = 104) consisting of 111 independent experiments were assessed following an intensive search of electronic databases. Commonly reported indicators of parturition (n = 38) were identified, and temporal trend graphs were generated for 13 of these changes. The results compare trends in behavioral and physiological changes across a variety of animal-related factors and identifies several reliable indicators of parturition for detection with sensors, namely calf grooming behavior, changes in rumination duration, and lying bouts. This synthesis of literature suggests that variability exists between individuals and thus, combining several calving indicators may result in a more broadly applicable and accurate detection of parturition.

The Role of Schlemm's Canal Endothelium Cellular Connectivity in Giant Vacuole Formation: A 3D Electron Microscopy Study.

Purpose: We investigated whether cellular connectivity between Schlemm's canal (SC) inner wall (IW) endothelium, and juxtacanalicular connective tissue (JCT), and between IW endothelial cells, plays a role in giant vacuole (GV) and pore formation by comparing perfusion- and immersion-fixed eyes. Methods: Normal human donor eyes (n = 4) were either immersion-fixed (0 mm Hg) or perfusion-fixed (15 mm Hg). Trabecular meshwork near SC was imaged using serial block-face scanning electron microscopy. A total of 12 IW cells from each group were 3D-reconstructed from ∼7040 electron micrographs and compared. In each cell, connections between IW cells and JCT cells/matrix were quantified; IW/IW connectivity was measured by cell border overlap length. GV volume, density, shape, and intracellular and paracellular pores were analyzed. Results: The mean number of IW/JCT cell-cell connections per cell significantly decreased (P < 0.01) while the summed GV volume per cell significantly increased (P < 0.01) in perfusion-fixed eyes compared to immersion-fixed eyes. Intracellular pores were observed in 14.6% of GVs in perfusion-fixed eyes and not observed in immersion-fixed eyes. The mean IW/IW overlap length per cell decreased (P < 0.01), and paracellular pores were found only in regions where IW/IW connectivity was minimal (overlap length = 0 µm) in perfusion-fixed eyes and not observed in immersion-fixed eyes. Conclusions: Our data suggest that changes in IW/JCT connectivity may be an important factor in the formation of larger GVs, and decreased IW/IW connectivity may promote paracellular pore formation. Targeting the IW/JCT and IW/IW connectivity may therefore be a potential strategy to regulate outflow resistance and IOP. .

Shorter scleral spur in eyes with primary open-angle glaucoma.

PURPOSE: We determined whether the scleral spur is shorter in primary open-angle glaucoma (POAG) eyes compared to age-matched normal eyes and whether the collapse of Schlemm's canal (SC) is more prevalent in eyes with a shorter scleral spur. METHODS: The anterior segments of normal (n = 20) and POAG eyes (n = 20) were fixed and processed for light microscopy. The scleral spur length, ratio of posterior trabecular meshwork (TM) insertion into the scleral spur to the posterior TM height, and the percentage of SC collapse were measured. Analysis using an existing mathematical model was conducted to estimate the distances that the scleral spur theoretically would move in vivo and to determine if these distances would be sufficient to keep SC open in POAG compared to normal eyes. RESULTS: The mean scleral spur length was significantly shorter in POAG eyes compared to normal eyes (P < 0.0001). A higher mean percentage of SC collapse was found in POAG eyes than in normal eyes (P < 0.0001). Estimated posterior movement of scleral spur in POAG eyes was less than sufficient to prevent the collapse of SC. A significant negative correlation was found between the posterior scleral spur movement and percent collapse of SC (P < 0.0001). CONCLUSIONS: A shorter scleral spur found in POAG eyes was associated with a higher percent of SC collapse. Our data suggest that a shorter scleral spur may be a risk factor in the development of POAG by being insufficient to hold SC open.

The potential for modification in cloning and vitrification technology to enhance genetic progress in beef cattle in Northern Australia.

Recent advances in embryology and related research offer considerable possibilities to accelerate genetic improvement in cattle breeding. Such progress includes optimization and standardization of laboratory embryo production (in vitro fertilization - IVF), introduction of a highly efficient method for cryopreservation (vitrification), and dramatic improvement in the efficiency of somatic cell nuclear transfer (cloning) in terms of required effort, cost, and overall outcome. Handmade cloning (HMC), a simplified version of somatic cell nuclear transfer, offers the potential for relatively easy and low-cost production of clones. A potentially modified method of vitrification used at a centrally located laboratory facility could result in cloned offspring that are economically competitive with elite animals produced by more traditional means. Apart from routine legal and intellectual property issues, the main obstacle that hampers rapid uptake of these technologies by the beef cattle industry is a lack of confidence from scientific and commercial sources. Once stakeholder support is increased, the combined application of these methods makes a rapid advance toward desirable traits (rapid growth, high-quality beef, optimized reproductive performance) a realistic goal. The potential impact of these technologies on genetic advancement in beef cattle herds in which improvement of stock is sought, such as in northern Australia, is hard to overestimate.

Evolutionary process of Bos taurus cattle in favourable versus unfavourable environments and its implications for genetic selection.

The evolutionary processes that have enabled Bos taurus cattle to establish around the globe are at the core to the future success of livestock production. Our study focuses on the history of cattle domestication including the last 60 years of B. taurus breeding programmes in both favourable and unfavourable environments and its consequences on evolution and fitness of cattle. We discuss the emergence of 'production diseases' in temperate production systems and consider the evolutionary genetics of tropical adaptation in cattle and conclude that the Senepol, N'Dama, Adaptaur and Criollo breeds, among others with similar evolutionary trajectories, would possess genes capable of improving the productivity of cattle in challenging environments. Using our own experimental evidence from northern Australia, we review the evolution of the Adaptaur cattle breed which has become resistant to cattle tick. We emphasize that the knowledge of interactions between genotype, environment and management in the livestock systems will be required to generate genotypes for efficient livestock production that are both economically and environmentally sustainable. Livestock producers in the 21st century will have less reliance on infrastructure and veterinary products to alleviate environmental stress and more on the animal's ability to achieve fitness in a given production environment.

Understanding foraging behaviour in spatially heterogeneous environments.

The role of stochasticity and spatial heterogeneity in foraging systems is investigated. We formulate a spatially explicit model which describes the behaviour of grazing animals in response to local information using simple stochastic rules. In particular the model reflects the biology in that decisions to move to a new location are based on visual assessment of the sward height in a surrounding neighbourhood, whilst the decision to graze the current location is based on the residual sward height and olfactory assessment of local faecal contamination. It is assumed that animals do not interact directly, but do so through modification of, and response to a common environment. Spatial heterogeneity is shown to have significant effects including reducing the equilibrium intake rate and increasing the optimal stocking density, and must therefore be taken into account by resource managers. We demonstrate the relationship between the stochastic spatial model and its non-spatial deterministic counterpart, and in the process derive a moment-closure approximation to the full process, which can be regarded as an intermediate, or pseudo-spatial model. The role of spatial heterogeneity is emphasized, and better understood by comparing the results obtained from each approach. The relative efficiency of random and directed searching behaviour in spatially heterogeneous environments is explored for both clean and contaminated pastures, and the impact of faecal avoidance behaviour assessed.