Weather and infectious disease in cattle

Correlation of Ambient Temperature With Feedlot Cattle Morbidity and Mortality in the Texas Panhandle

Anecdotal data would suggest that weather patterns influence beef cattle health in feedyards, and cattle producers often associate the seasonality of some illnesses with changes in environmental temperatures. However, to our knowledge, there is little information from large-scale feeding operations and precision weather stations that establishes a link or lack thereof between weather patterns and cattle health. Additionally, we are unaware of any studies correlating other weather parameters with animal health data. Therefore, the objective of this study was to test for associations between monthly temperature variation and animal morbidity/mortality in feedlots in the Texas Panhandle. Weather data was collected from a Texas Tech University Mesonet weather station in close proximity to 19 beef cattle feedyards in the Texas Panhandle. Additionally, near real-time morbidity and mortality data was collected from those yards from 2015 to 2018. These data document a seasonal pattern relative to cattle morbidity and mortality with most health events occurring from November to January. This pattern is differentiated when comparing morbidity and mortality by listed causation (e.g., respiratory, digestive, other), and the majority of deaths over the entire time course were attributed to respiratory disease. Most cattle morbidity was documented in the winter months, most of which were classified as respiratory disorders. Additionally, an increase in health events was observed as the population of the feedyard increased. However, the overall effects of ambient temperature on cattle health were minimal and the two may not be causally linked. The initial overview of the relationships documented in this manuscript may warrant further stratification and exploration.

Climatic influence on anthrax suitability in warming northern latitudes

Climate change is impacting ecosystem structure and function, with potentially drastic downstream effects on human and animal health. Emerging zoonotic diseases are expected to be particularly vulnerable to climate and biodiversity disturbance. Anthrax is an archetypal zoonosis that manifests its most significant burden on vulnerable pastoralist communities. The current study sought to investigate the influence of temperature increases on geographic anthrax suitability in the temperate, boreal, and arctic North, where observed climate impact has been rapid. This study also explored the influence of climate relative to more traditional factors, such as livestock distribution, ungulate biodiversity, and soil-water balance, in demarcating risk. Machine learning was used to model anthrax suitability in northern latitudes. The model identified climate, livestock density and wild ungulate species richness as the most influential features in predicting suitability. These findings highlight the significance of warming temperatures for anthrax ecology in northern latitudes, and suggest potential mitigating effects of interventions targeting megafauna biodiversity conservation in grassland ecosystems, and animal health promotion among small to midsize livestock herds.

Using Bayesian networks to explore the role of weather as a potential determinant of disease in pigs

Many pathogens are sensitive to climatic variables and this is reflected in their seasonality of occurrence and transmission. The identification of environmental conditions that influence disease occurrence can be subtle, particularly considering their complex interdependencies in addition to those relationships between climate and disease. Statistical treatment of environmental variables is often dependent on their correlations and thus descriptions of climate are often restricted to means rather than accounting for the more precise aspects (including mean, maximum, minimum, variability). Here we utilize a novel multivariate statistical modelling approach, additive Bayesian network (ABN) analyses, to identify the inter-linkages of different weather variables to better capture short-term environmental conditions that are important drivers of disease. We present a case study that explores weather as a driver of disease in livestock systems. We utilize quality assurance health scheme data on ten major diseases of pigs from 875 finishing pig herds distributed across the United Kingdom over 7 years (2005-2011). We examine the relationship between the occurrence of these pathologies and contemporary weather conditions measured by local meteorological stations. All ten pathologies were associated with at least 2 other pathologies (maximum 6). Three pathologies were associated directly with temperature variables: papular dermatitis, enzootic pneumonia and milk spots. Latitude was strongly associated with multiple pathologies, though associations with longitude were eliminated when clustering for repeated observations of farms was assessed. The identification of relationships between climatic factors and different (potentially related) diseases offers a more comprehensive insight into the complex role of seasonal drivers and herd health status than traditional analytical methods.

Temporal and spatial distribution of cattle anthrax outbreaks in Zimbabwe between 1967 and 2006

This retrospective study aimed to assess the spatial and temporal distribution of anthrax and to identify risk areas in Zimbabwe. The data were extracted from the monthly and annual reports of the Division of Livestock Production and Veterinary Services for the period 1967 to 2006. The data were analyzed in relation to temporal and spatial factors. The hot-dry season was found to be significantly (X (2)=847.8, P<0.001) associated with the occurrence of anthrax in cattle, and the disease was found to be approximately three times more likely to occur during this season compared to other seasons. Anthrax outbreaks demonstrated a gradual temporal increase from an annual mean of three outbreaks for the 5-year period (1967-1971) to 42 for the 5-year period (2002-2006). Similarly, the data demonstrated a spatial increase in the number of districts affected by anthrax between 1967 and 2006, with 12 districts affected for the 10-year period (1967-1976) that expanded to 42 districts for the 10-year period (1997-2006). The majority of outbreaks (83.7%) were recorded in rural areas, and 11 districts were found to be at a higher risk than others. There is need to develop differential vaccination strategy, other control strategies and preventive recommendations to reduce anthrax in high-risk districts. In the medium- to low-risk districts, maintenance of effective surveillance systems and improvement of awareness is very important to detect and contain outbreaks early.

The effect of air filtration on air hygiene and pig performance in early-weaner accommodation

The effects of an internal recirculating air filter on air hygiene and pig performance were studied using two groups each of 100 early-weaned pigs from a commercial herd. The two groups were housed in separate rooms under identical conditions except that one room contained a recirculating air filter. Five trials were carried out, but the same records were not kept in all trials. The air throughput of the filter was similar to the installed ventilation capacity (0·9 m3/s). The filter material nominally removed particles > 5 μm. Distribution ducts discharged the filtered air downwards over the pigs' lying area at a velocity of 0·3 m/s. At locations close to the pigs, the most representative proportional reductions of total particles, dust mass, and bacterial colony-forming particles were 0·58 (P< 0·01), 0·73 (P< 0·01), and 0·51 (P< 0·01), respectively. No differences in growth rate or health of pigs after 3 to 4 weeks were observed between the rooms but the pigs originating from the room containing the air filter reached a marketable state 6 to 8 days earlier than the control group pigs on the three occasions that this aspect was monitored (P< 0·0·01).

Effects of air temperature, air velocity and feeding level on apparent digestibility, water intake, water loss and growth in calves given a milk substitute diet

Six groups of eight 2-day-old calves were placed successively in a controlled environment chamber. Three groups were exposed to air temperatures of 10° and 25°C. A liquid diet of skimmed-milk substitute and 4 I/day of drinking (free) water was offered to each calf. Within each group, calves were allocated to either a low (<0·2 m/s) or a high (>3 m/s) air velocity and to either a low (30 g dry matter (DM) per kg M0·75per day) or a high (40 g DM per kg M0·75per day) feeding level. At 8 days of age the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·77 (s.e. 0·126) and 0·82 (s.e. 0·126) respectively (P > 0·05). The apparent digestibilities of DM were greater at the low feeding level with low air velocity than for either this feeding level with high air velocity or the high feeding level at both air velocities (P< 0·05) between which there was no significant difference (P > 0·05). At 8 days of age there were significant air temperature × air velocity (P< 001) and air velocity × feeding level interactions in the intake of free water (P< 005). There was a significant air temperature × feeding level interaction for total water intake (P< 0·05). Urinary water loss relative to total water intake was significantly greater at the low air velocity than at the high air velocity (P< 0·05).

In a further two groups of eight calves given 30 g DM per kg M 75 per day at 8 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·71 (s.e. 0·020) and 0·90 (s.e. 0·013) respectively (P< 0·01). In the same calves given 40 g DM per kg M0·75per day at 20 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·89 (s.e. 0·009) and 0·93 (s.e. 0·011) respectively (P< 0·05). The free and total water intakes, the ratios of (total water intake-faecal water loss): total water intake and the urinary losses of water were significantly greater at the air temperature of 25°C than at 10°C (P< 0·05). Live-weight gains were lower at 10°C than at 25°C (P< 0·01).

The results suggested that air temperature, air velocity and feeding level can affect the health and growth of calves less than 4 weeks of age.

Avoiding hypothermia, an intervention to prevent morbidity and mortality from pneumonia in young children

Observations and experiments in animals and human beings grant plausibility to the hypothesis that hypothermia is a risk factor for pneumonia. Exposure of body to cold stress causes alterations in the systemic and local defenses against respiratory infections, favoring the infection by inhalation of pathogens normally present in the oropharynx. Neonates and young infants with hypothermia have an increased risk of death; however, there is no strong demonstration that hypothermia leads to pneumonia in these children. Studies that properly addressed the problem of confounding variables have shown an association between cold weather and pneumonia incidence. Probably the strongest evidence that supports the plausibility of the hypothesis is provided by the controlled comparison between patients with traumatic brain injury treated with hypothermia and those treated under normal body temperature. The association between exposure to cold and pneumonia is strong enough to warrant further research focused in young children in developing countries.

The ecology of Bacillus anthracis

The global distribution of anthrax is largely determined by soils with high calcium levels and a pH above 6.1, which foster spore survival. It is speculated that the spore exosporium probably plays a key part by restricting dispersal and thereby increasing the probability of a grazing animal acquiring a lethal dose. 'Anthrax Seasons' are characterized by hot-dry weather which stresses animals and reduces their innate resistance to infection allowing low doses of spores to be infective. Necrophagic flies act as case-multipliers and haemophagic flies as space-multipliers; the latter are aided by climatic factors which play a key part in whether epidemics occur. Host death is a function of species sensitivity to the toxins. The major function of scavengers is to open the carcass, spill fluids, and thereby aid bacilli dispersal and initiate sporulation. In the context of landscape ecology viable spore distribution is a function of mean annual temperature, annual precipitation, elevation, mean NDVI, annual NDVI amplitude, soil moisture content, and soil pH.

Epidemiological investigation of the influence of environmental risk factors on respiratory diseases in swine--a literature review

The influence of environmental and management factors on respiratory diseases in pigs is reviewed from an epidemiological point of view. The suitability of methods for the investigation of risk factors is discussed including aspects of study design, case definition, exposure assessment and data analysis. The results of published studies suggest a causal web of factor interaction, the analysis of which provides considerable challenges for current epidemiological techniques. New approaches to the problem should be further explored in the future in order to provide reliable advice to decision makers.

Characterization of a 54-kDa heat-shock-inducible protein of Pasteurella haemolytica

Growth-condition-dependent antigens play a role in the virulence or protective capacity of many organisms. Enhanced production of an approximately 54-kDa protein was detected in heat-shocked cultures of Pasteurella haemolytica. The heat-shock-inducible protein cross-reacted with antibodies to 60-kDa heat-shock proteins of Mycobacterium tuberculosis, Chlamydia, and Escherichia coli GroEL. A probe containing the E. coli groEL operon hybridized with fragments of P. haemolytica chromosomal DNA on Southern blots. Immunoblots of the 54-kDa protein using serum from 20 calves that were challenged experimentally with P. haemolytica resulted in band densities that were significantly different between calves with high and low lesion scores. Results of the study suggest that the 54-kDa heat-shock protein may be a growth-condition-dependent immunogen that is one component of resistance to pneumonic pasteurellosis.

The effects of age, environmental temperature and relative humidity on the bacterial flora of the upper respiratory tract in calves

The effects of age, environmental temperature and relative humidity on the bacterial flora of the nose and trachea of calves were investigated by sequential sampling of three groups each of eight Friesian-Holstein male calves kept in three different environmental conditions. All calves were vaccinated with a live attenuated vaccine against infectious bovine rhinotracheitis (IBR) when they were 12 weeks old. Nasal and tracheal swabs were collected at 14-day intervals for bacteriological examinations. The upper respiratory tract of calves started to be colonized by various species of bacteria within the first day of life. Although they were born at different periods of the year, the calves in all three groups had similar bacterial loads in their noses and tracheas when they were 1 day old (P greater than 0.05). The total bacterial colony forming units (BCFU) were highly variable from calf to calf and from one time of sampling to another. Despite these variations, there were age-related increases in the total BCFU in nasal and tracheal swabs in all experiments. These increases were influenced by environmental temperature. Vaccination of the calves with a live IBR vaccine appeared to enhance the bacterial colonization of the upper respiratory tract.

Effects of chronic heat and cold stressors on plasma immunoglobulin and mitogen-induced blastogenesis in calves

Fifty-six Holstein calves were used to investigate effects of heat and cold stressors on mitogen-induced blastogenesis of isolated peripheral blood mononuclear cells and immunoglobulins G1 and M in blood plasma. Calves were exposed to constant hot (35 degrees C), constant cold (-5 degrees C), or thermoneutral (23 degrees C) ambient conditions in environmentally-controlled chambers. Immune responses were measured soon after introduction into environmental chambers (3 days) and after various degrees of adaptation (7 and 14 days). Mortality was greater among heat- and cold-exposed calves than among thermoneutral calves. Neither heat nor cold exposure had a direct effect on blastogenesis of peripheral blood mononuclear cells by phytohemagglutinin or concanavalin A. Plasma from heat- and cold-exposed calves then was incorporated into the culture medium at a final concentration of 5% and tested in a mitogenesis assay on peripheral blood mononuclear cells from a single healthy donor. Plasma from heat-exposed calves consistently enhanced tritiated thymidine incorporation into normal peripheral blood mononuclear cells by phytohemagglutinin and concanavalin A as compared to plasma from cold-exposed calves. After heat exposure for 3 to 14 days, immunoglobulin G1 averaged 27% less in heat-exposed calves than in calves that were held at thermoneutrality, but M was unaffected. Cold exposure did not have a consistent effect on G1 or M. These data demonstrate that chronic heat and cold stressors affect calves by altering both antibody- and cell-mediated immunity.