Slaughter Of Infected Animals Research Articles

Knowledge, attitude and practice related to anthrax among livestock farmers in West Kazakhstan.

Anthrax is the most prioritized zoonotic disease in Kazakhstan due to its threatening potential to the public health and agricultural sector. Sporadic anthrax outbreaks are being reported annually among human and livestock populations throughout the country, with the highest frequency occurring in West Kazakhstan. A cross-sectional study was conducted using a survey-based face-to-face interview. From January to May 2022, 489 randomly selected participants were surveyed in 6 districts of the Baiterek province in West Kazakhstan oblast to evaluate the knowledge, attitude and practice (KAP) regarding anthrax among community members. This is the first KAP study conducted relating to outbreaks of anthrax in Kazakhstan. In this study, most participants (74%) surveyed were males, and 40% of respondents had a secondary level education. Overall, 91% of the community respondents were engaged in agriculture and livestock rearing. Among these community members, cattle rearing was the most common (67%) occupation compared to other livestock species. Additionally, over a 50% of the population studied had no knowledge about the zoonotic nature of the disease, and about 82% and 87% of respondents were unaware of any animal and human anthrax symptoms, respectively. About 70% of the respondents were interested in vaccinating their livestock against anthrax. Individuals aged 45-54 displayed notably higher animal vaccination rates (45%; 95% CI: 38.4-52.0; p<0.025) compared to those aged 25-34 and 65-74. Respondents residing in the Beles district (20%; 95% CI: 17.1-24.7; p<0.005) exhibited a significantly higher level of awareness concerning the fatality of anthrax in contrast to participants from Bolashak. Roughly 61% of respondents held the belief that anthrax is a lethal disease. An overwhelming majority of the survey participants (99%) affirmed their non-participation in the slaughter of infected animals. The findings of this study indicate that KAP among community members relating to anthrax is low and requires swift implementation of education programmes in building awareness of anthrax under the One Health approach, especially in anthrax prone regions.

Increased Vaccination Diversity Leads to Higher and Less-Variable Neutralization of TBE Viruses of the European Subtype.

Tick-borne encephalitis (TBE) is an infectious disease of the central nervous system. The causative agent is the tick-borne encephalitis virus (TBEV), which is most commonly transmitted by tick bites, but which may also be transmitted through the consumption of raw dairy products or, in rare instances, via infected transfusions, transplants, or the slaughter of infected animals. The only effective preventive option is active immunization. Currently, two vaccines are available in Europe-Encepur® and FSME-IMMUN®. In Central, Eastern, and Northern Europe, isolated TBEV genotypes belong mainly to the European subtype (TBEV-EU). In this study, we investigated the ability of these two vaccines to induce neutralizing antibodies against a panel of diverse natural TBEV-EU isolates from TBE-endemic areas in southern Germany and in regions of neighboring countries. Sera of 33 donors vaccinated with either FSME-IMMUN®, Encepur®, or a mixture of both were tested against 16 TBEV-EU strains. Phylogenetic analysis of the TBEV-EU genomes revealed substantial genetic diversity and ancestry of the identified 13 genotypic clades. Although all sera were able to neutralize the TBEV-EU strains, there were significant differences among the various vaccination groups. The neutralization assays revealed that the vaccination using the two different vaccine brands significantly increased neutralization titers, decreased intra-serum variance, and reduced the inter-virus variation.

The Biosafety Research Road Map: The Search for Evidence to Support Practices in the Laboratory-Bacillus anthracis and Brucella melitensis.

Brucella melitensis and Bacillus anthracis are zoonoses transmitted from animals and animal products. Scientific information is provided in this article to support biosafety precautions necessary to protect laboratory workers and individuals who are potentially exposed to these pathogens in the workplace or other settings, and gaps in information are also reported. There is a lack of information on the appropriate effective concentration for many chemical disinfectants for this agent. Controversies related to B. anthracis include infectious dose for skin and gastrointestinal infections, proper use of personal protective equipment (PPE) during the slaughter of infected animals, and handling of contaminated materials. B. melitensis is reported to have the highest number of laboratory-acquired infections (LAIs) to date in laboratory workers. A literature search was conducted to identify potential gaps in biosafety and focused on five main sections including the route of inoculation/modes of transmission, infectious dose, LAIs, containment releases, and disinfection and decontamination strategies. Scientific literature currently lacks information on the effective concentration of many chemical disinfectants for this agent and in the variety of matrices where it may be found. Controversies related to B. anthracis include infectious dose for skin and gastrointestinal infections, proper use of PPE during the slaughter of infected animals, and handling contaminated materials. Clarified vulnerabilities based on specific scientific evidence will contribute to the prevention of unwanted and unpredictable infections, improving the biosafety processes and procedures for laboratory staff and other professionals such as veterinarians, individuals associated with the agricultural industry, and those working with susceptible wildlife species.

Spread of Aujeszky’s disease among wild boars and domestic pigs in Ukraine

Aujeszky’s disease, also known as pseudorabies is an acute infectious viral disease in a variety of mammals caused by Suid herpesvirus 1, a member of the subfamily Alphaherpesvirinae and the family Herpesviridae. This virus causes significant economic losses in agriculture of numerous countries. In particular, in pig farming, the main losses are currently associated with restrictions of international trade, as well as the cost of vaccination or slaughter of infected animals. The main reservoirs species of this disease are considered to be wild boars and domestic pigs. So, in this article the authors performed a comparative retrospective analysis of the prevalence of Aujeszky’s disease among these species in Ukraine over 2009–2020 by systematizing and analyzing the epizootic data and results of serological studies. As a result of the conducted research, there is a clear trend that shows the reduction in the number of locations in Ukraine (farms, households, etc.) with domestic pigs affected by Aujeszky’s disease. Thus, in 2009 four such farms were found, and in 2018 – only one. During 2014–2016 and 2019–2020, affected farms and locations were not registered for this disease. In total, 21 such points with infected pigs were registered during the analyzed period. As for wild boars, during the analyzed 12 years, locations with animals affected by Aujeszky’s disease were registered only in 2013 and 2014 (two and one, respectively). It should be noted that all of those with infected wild boars were found in the AR Crimea. For the twelve years, the number of tested sera samples from domestic pigs amounted to 378,678 (7.4% were positive) and from wild boars – 9,052 (19.8% were positive). As a result of comparative geographical analysis of the obtained data on the detection of specific humoral antibodies to the Aujeszky’s disease virus among both species for 12 years in the regions of Ukraine, there is no established clear correlation between the spread of the disease among wild boars and domestic pigs. Thus, the highest seroprevalence rates among wild boars were observed in the northern and northeastern parts of Ukraine, and in domestic pigs, on the contrary, in the southern and central parts of this country. It should be noted, that since 2014 the number of serological tests among both species for carriers of Aujeszky’s disease has significantly decreased.

Epidemiology of brucellosis in Dehloran, Ilam province, between 2015 and 2019, A cross sectional, epidemiologic study

Background & objective , Brucellosis is a zoonotic disease whose most common complications include intermittent fever, headache, fatigue, weight loss, night sweats, joint pain, osteomyelitis, spondylitis, peripheral arthritis, sacroiliitis, etc. In this study, the epidemiology of brucellosis in Dehloran, Iran between 2015 and 2019 was studied. Methods, This study was conducted from February 2015 to November 2018 in Dehloran, Ilam province, Iran. Patients with certain symptoms such as pain were selected and referred to the lab. The samples were collected and investigated by Wright test. Results, Brucellosis in Dehloran is an occupational disease with most cases occurring in livestock breeders followed by housewives. Most cases are due to the consumption of dairy products such as milk. Conclusion, In general, it can be argued that in spite of the high incidence of the disease in this region, adequate attention has not yet been paid to it. Due to the occupational nature of the disease in the region, vaccination, disease surveillance and slaughter of infected animals are also recommended. Livestock should also be purchased through the cooperatives of livestock breeders and transported to dairy factories so that contaminated milk will not be delivered to the public.

Development of a diagnostic compatible BCG vaccine against Bovine tuberculosis

Bovine tuberculosis (BTB) caused by Mycobacterium bovis remains a major problem in both the developed and developing countries. Control of BTB in the UK is carried out by test and slaughter of infected animals, based primarily on the tuberculin skin test (PPD). Vaccination with the attenuated strain of the M. bovis pathogen, BCG, is not used to control bovine tuberculosis in cattle at present, due to its variable efficacy and because it interferes with the PPD test. Diagnostic tests capable of Differentiating Infected from Vaccinated Animals (DIVA) have been developed that detect immune responses to M. bovis antigens absent in BCG; but these are too expensive and insufficiently sensitive to be used for BTB control worldwide. To address these problems we aimed to generate a synergistic vaccine and diagnostic approach that would permit the vaccination of cattle without interfering with the conventional PPD-based surveillance. The approach was to widen the pool of M. bovis antigens that could be used as DIVA targets, by identifying antigenic proteins that could be deleted from BCG without affecting the persistence and protective efficacy of the vaccine in cattle. Using transposon mutagenesis we identified genes that were essential and those that were non-essential for persistence in bovine lymph nodes. We then inactivated selected immunogenic, but non-essential genes in BCG Danish to create a diagnostic-compatible triple knock-out ΔBCG TK strain. The protective efficacy of the ΔBCG TK was tested in guinea pigs experimentally infected with M. bovis by aerosol and found to be equivalent to wild-type BCG. A complementary diagnostic skin test was developed with the antigenic proteins encoded by the deleted genes which did not cross-react in vaccinated or in uninfected guinea pigs. This study demonstrates the functionality of a new and improved BCG strain which retains its protective efficacy but is diagnostically compatible with a novel DIVA skin test that could be implemented in control programmes.

Finding factors associated with nasal shedding of Mycobacterium tuberculosis variant bovis in wild boar

bovine TB (bTB) is an infectious disease – caused by Mycobacterium tuberculosis variant bovis – that affects several species of animals. The World Health Organization (WHO) classifies bTB as a...

Seroprevalence of brucellosis in flocks of goats in Kaduna State, Northwestern Nigeria

Brucellosis is a bacterial contagious disease of animals and humans caused by bacteria of genus Brucella. A cross sectional study was carried out to determine the seroprevalence of brucellosis in flocks of goats in Maigana agro-ecological zone of Kaduna State. This study was aimed to determine the seroprevalence of brucellosis and the risk factors influencing the occurrence of Brucella specie in goats in Kaduna State. Total of four hundred (400) blood samples were tested for brucellosis using Rose Bengal Plate Test (RBPT) and Competitive Enzyme Immunosorbent Assay (ELISA). Out of the 400 sera samples tested, 48 (12.0%) and 24 (6.0%) were seropositive by RBPT and cELISA respectively. Out of the 147 male goats tested, 10 (6.8%) and 6 (4.1%) were seropositive, while out of 253 female goats tested, 38 (15.0%) and 18 (7.1%) were seropositive using RBPT and cELISA. There was statistically significant association (p&lt;0.05) between the sex of goats and RBPT, but there was no statistically significant association (p&gt;0.05) between the sex of goats and cELISA. Based on age distribution, the seroprevalence 13.4 and 6.3% by RBPT and cELISA were recorded in the age group 2 to 4 years. Based on breed distribution, the highest seroprevalence 13.4 and 8.1% by RBPT and cELISA were recorded in Sokoto Red. There was no statistically significant association (p&gt;0.05) between the age and breed of goats with RBPT and cELISA. The study concludes that brucellosis is prevalent in the flocks of goat in the study area. The high seroprevalence of brucellosis is of economic and public health concern because the pastoralists regard goats’ milk to have exceptional medicine potentials. Therefore, brucellosis may be prevented via vaccination of domestic livestock, serologic testing, quarantine of herds, and slaughter of infected animals.

Epidemiologic, clinical, and laboratory characteristics of childhood brucellosis

Brucellosis is endemic in Iran. Children constitute 20-25% of cases. We determined clinical, laboratory, and epidemiologic characteristics of pediatric brucellosis patients hospitalized at the Children's Medical Center from May 2011 to December 2016. Medical records were reviewed retrospectively. For each patient, aquestionnaire was provided containing demographic characteristics (sex, age, nationality, date of admission, city of residence, history of ingestion of unpasteurized dairy products, family history of brucellosis, history of contact with suspicious animals) and clinical information (signs and symptoms, laboratory findings, history of disease relapse, treatment). Included were 43patients diagnosed with brucellosis (26males, 60.5%; age 1-13years, mean ± SD: 7.02 ± 3.5). Ahistory of ingestion of raw or unpasteurized dairy products was present in 88% (N = 38) and 11patients (26%) had had contact with asuspicious animal. Highest frequencies of brucellosis were recorded in 2013 (N = 10, 23%) and 2015 (N = 11, 26%). Most cases were admitted in the summer (N = 14, 33%) and spring (N = 12, 28%). Fever (N = 39, 91%), arthralgia (N = 33, 77%), and malaise (N = 33, 77%) were the main complaints. Anemia (65%), lymphocytosis (51%), and elevated erythrocyte sedimentation rate (86%) and C‑reactive protein (67%) were the most prominent blood anomalies. Blood culture was positive in 30% (N = 11/37), bone marrow culture in 31% (N = 4/11). Apositive Wright, Coombs Wright, and 2 ME test was observed in 67%(N = 29), 92% (N = 34/37), and 85% (N = 34/40) of cases, respectively. Median length of antibiotic therapy was 12weeks (2-24weeks). The most frequent drug regimen was combined trimethoprim-sulfamethoxazole and rifampicin (N = 24, 56%). Relapse occurred in 9patients (21%), there were no deaths. Physicians should be aware of the manifestations, diagnosis, and treatment protocols of childhood brucellosis. Control programs and preventive measures, e.g., regular examination of domestic animals, mass vaccination of livestock, slaughter of infected animals, control of animal trade and migration, pasteurization of milk and milk products, training and increased public awareness of the dangers of consumption of unpasteurized dairy products, are highly recommended.

Brucellosis: Improved Diagnostics and Vaccine Insights from Synthetic Glycans.

ConspectusBrucellosis is a serious zoonotic bacterial disease that is ranked by the World Health Organization among the top seven “neglected zoonoses” that threaten human health and cause poverty. It is a costly, highly contagious disease that affects ruminants, cattle, sheep, goats, and other productive animals such as pigs. Symptoms include abortions, infertility, decreased milk production, weight loss, and lameness. Brucellosis is also the most common bacterial disease that is transmitted from animals to humans, with approximately 500 000 new human cases each year. Detection and slaughter of infected animals is required to eradicate the disease, as vaccination alone is currently insufficient. However, as the most protective vaccines compromise serodiagnosis, this creates policy dilemmas, and these often result in the failure of eradication and control programs. Detection of antibodies to the Brucella bacterial cell wall O-polysaccharide (OPS) component of smooth lipopolysaccharide is used in diagnosis of this disease, and the same molecule contributes important protective efficacy to currently deployed veterinary whole-cell vaccines. This has set up a long-standing paradox that while Brucella OPS confers protective efficacy to vaccines, its presence results in similar antibody profiles in infected and vaccinated animals. Consequently, differentiation of infected from vaccinated animals (DIVA) is not possible, and this limits efforts to combat the disease. Recent clarification of the chemical structure of Brucella OPS as a block copolymer of two oligosaccharide sequences has provided an opportunity to utilize unique oligosaccharides only available via chemical synthesis in serodiagnostic tests for the disease. These oligosaccharides show excellent sensitivity and specificity compared with the native polymer used in current commercial tests and have the added advantage of assisting discrimination between brucellosis and infections caused by several bacteria with OPS that share some structural features with those of Brucella. During synthesis and immunochemical evaluation of these synthetic antigens, it became apparent that an opportunity existed to create a polysaccharide–protein conjugate vaccine that would not create antibodies that give false positive results in diagnostic tests for infection. This objective was reduced to practice, and immunization of mice showed that antibodies to the Brucella A antigen could be developed without reacting in a diagnostic test based on the M antigen. A conjugate vaccine of this type could readily be developed for use in humans and animals. However, as chemical methods advance and modern methods of bacterial engineering mature, it is expected that the principles elucidated by these studies could be applied to the development of an inexpensive and cost-effective vaccine to combat endemic brucellosis in animals.

Estimation of the Infection Window for the 2010/2011 Korean Foot-and-Mouth Disease Outbreak

ObjectivesThis study aims to develop a method for calculating infection time lines for disease outbreaks on farms was developed using the 2010/2011 foot-and-mouth disease (FMD) epidemic in the Republic of Korea. MethodsData on farm demography, the detection date of FMD, the clinical history for the manifestation of lesions, the presence of antibodies against FMD virus (including antibodies against the structural and nonstructural proteins of serotype O), vaccination status (O1 Manisa strain), the number of reactors and information on the slaughter of infected animals were utilized in this method. ResultsBased on estimates of the most likely infection date, a cumulative detection probability that an infected farm would be identified on a specific day was determined. Peak infection was observed between late December and early January, but peak detection occurred in mid-January. The early detection probability was highest for pigs, followed by cattle (dairy, then beef) and small ruminants. Nearly 90% of the infected pig farms were detected by Day 11 post-infection while 13 days were required for detection for both dairy and beef cattle farms, and 21 days were necessary for small ruminant (goat and deer) farms. On average, 8.1 ± 3.1 days passed prior to detecting the presence of FMD virus on a farm. The interval between infection and detection of FMD was inversely associated with the intensity of farming. ConclusionThe results of our study emphasize the importance of intensive clinical inspection, which is the quickest method of detecting FMD infection and minimizing the damage caused by an epidemic.

Screening of recombinant proteins as antigens in indirect ELISA for diagnosis of bovine tuberculosis

Bovine tuberculosis is an important infectious disease caused by Mycobacterium bovis, which is responsible for considerable economic losses. This disease constitutes a serious public health problem. Control programs in most countries, including Brazil, are based on the identification and slaughter of infected animals, as defined by the skin tuberculin test, which has its constraints. In the present study, the recombinant proteins CFP-10, ESAT-6, Mb0143, MPB83, PE5, PE13, TB10.4, TB15.3 and a chimera of ESAT-6/MPB70/MPB83 (fusion protein) were tested as ELISA antigens for the diagnosis of bovine tuberculosis. The proteins were produced in Escherichia coli, purified and tested in ELISAs with sera from 126 cattle having tested negative in the comparative intradermal tuberculin test (CITT) and 107 sera from cattle having tested positive in the CITT. Also, 236 sera from two BTB-free beef cattle herds were tested. Among the proteins tested, only the ESAT-6/MPB70/MPB83 chimera demonstrated satisfactory agreement with the CITT (kappa index: 0.688), reflecting in 83.2% sensitivity and 86.5% specificity. The ELISA absorbances of the cattle sera from BTB-free herds showed similar levels to those of CITT positive cattle, probably as the result of successive skin tuberculinizations to define the BTB-free status of the herds. However, the ELISA with the ESAT-6/MPB70/MPB83 chimera was useful to discriminate BTB positive and negative cattle in herds prior to the tuberculin skin test.

Bluetongue vaccines: the past, present and future

Bluetongue (BT) is a noncontagious and arboviral disease of both domestic and wild ruminants. The disease is enzootic in areas where reservoirs (cattle and wild ruminants) and vectors exist for the BT virus (BTV). A total of 24 BTV serotypes have been recognized worldwide. The major control measures include restriction of animal movement, vector control applying insecticides, slaughter of infected animals and vaccination. Prophylactic immunization of sheep against BT is the most practical and effective control measure to combat BT infection. At present, attenuated vaccines are used in the Republic of South Africa, the USA and other countries. However, EU countries were using attenuated vaccines, only recently shifting to inactivated vaccines owing to their safety and efficacy. In India, inactivated vaccines are in experimental stages and are expected to be on the market shortly. Inactivated vaccines generate serotype-specific long-lasting protective immunity after two injections, and may help in controlling epidemics. Differentiating infected from vaccinated animals (DIVA) is theoretically possible with inactivated vaccines but has not yet been developed, whereas the attenuated live vaccines are not candidates for DIVA. Attenuated live vaccines are efficacious but safety issues are of great concern. New-generation vaccines (subunit, virus-like particles, core-like particles and vectored) can be employed for DIVA. Recombinant vaccines, which generate cross-protection against multiple BTV serotypes, have great potential in BT vaccine regimens. Furthermore, new-generation vaccines are safe and efficacious experimentally, but large-scale field trials are warranted. Alternative areas, such as antivirals, siRNA, interferon and nanotechnology, may be of future use in the control of BT. We give an overview of BT vaccines, starting from conventional to recent developments, and their feasibility in controlling BT infection.

Temporal and Spatial Distributions of Foot-and-Mouth Disease Under Three Different Strategies of Control and Eradication in Colombia (1982–2003)

Outbreaks of foot-and-mouth disease (FMD) from January 1982 through December 2003 were used to examine variations in serotype- and species-specific risk for three control programmes in Colombia: (1982-1983) vaccination, using an aluminium hydroxide, saponin adjuvant, required but not enforced; (1984-1996) vaccination, using an oil double-emulsion adjuvant, required but not enforced; and (1997-2003) enforced vaccination, using an oil double-emulsion adjuvant, restricted animal movement enforced, and slaughter of infected animals. Hypotheses were tested for trend, cyclicity and seasonality in FMD occurrence, and for species- and serotype-specific differences in morbidity and case-fatality. The spatial density of outbreaks was estimated by kernel smoothing. The frequency of outbreaks decreased most between 1984 and 1996 (p < 0.01) for serotype A and between 1997 and 2003 (p < 0.01) for serotype O. Outbreaks occurred in cycles of 3-4 years for both serotypes (p < 0.05). Morbidity was not significantly different in pigs from that in cattle for serotype A-associated outbreaks (p = 0.314), but was higher in pigs than in cattle (p = 0.019) for serotype O-associated outbreaks. For both serotypes, case-fatality was higher for pigs than for cattle (p < 0.009). Temporal variation in FMD incidence provided insight into the expected evolution of FMD control for countries with similar conditions and where FMD is endemic.

Use and abuse of mathematical models : an illustration from the 2001 foot and mouth disease epidemic in the United Kingdom

Foot and mouth disease (FMD) is a major threat, not only to countries whose economies rely on agricultural exports, but also to industrialised countries that maintain a healthy domestic livestock industry by eliminating major infectious diseases from their livestock populations. Traditional methods of controlling diseases such as FMD require the rapid detection and slaughter of infected animals, and any susceptible animals with which they may have been in contact, either directly or indirectly. During the 2001 epidemic of FMD in the United Kingdom (UK), this approach was supplemented by a culling policy driven by unvalidated predictive models. The epidemic and its control resulted in the death of approximately ten million animals, public disgust with the magnitude of the slaughter, and political resolve to adopt alternative options, notably including vaccination, to control any future epidemics. The UK experience provides a salutary warning of how models can be abused in the interests of scientific opportunism.

‘Flames and fear on the farms’: controlling foot and mouth disease in Britain, 1892–2001*

Abstract For over a century, the British government has pursued a policy of national freedom from foot and mouth disease (F.M.D.), a highly contagious disease of cloven-footed animals. One of the cornerstones of this policy was the slaughter of infected animals. However, on several occasions – most notably in 2001 – slaughter struggled to contain F.M.D., and provoked widespread criticism and calls for policy change. Drawing upon a range of previously unexamined sources, this article examines the history of F.M.D. in Britain, in an attempt to explain the twenty-first-century persistence of a Victorian disease control policy.

Mycobacterial diseases of deer

The most significant mycobacterial diseases of free-living, captive and farmed deer are bovine tuberculosis, caused by Mycobacterium bovis, Johne's disease (paratuberculosis), caused by Mycobacterium avium subsp paratuberculosis (basonym M. paratuberculosis), and avian tuberculosis, caused principally by M. avium subsp avium. The first case of M. bovis infection in farmed deer was identified in New Zealand in 1978. In 1983, a voluntary scheme was introduced in New Zealand to control tuberculosis in farmed deer, followed by a compulsory tuberculosis control scheme in 1990. The primary control measure is the slaughter of infected animals, detected by skin testing and blood testing, together with movement control and vector control. The number of infected deer herds peaked in the mid 1990s at over 160 herds, but by 30 June 2002 this had been reduced to 79 (1.45%), and to 67 (1.23%) by June 2003. Deer-to-deer transmission occurs, but the majority of herd breakdowns are believed to be from infected vectors. Factors likely to affect the susceptibility of deer include age, environment, population density, exposure and genetics. Avian tuberculosis occasionally causes clinical disease in wild, captive and farmed deer in New Zealand and overseas. Mycobacterium intracellulare, and subspecies of M. avium other than M. paratuberculosis, are widespread throughout New Zealand and are thought to be largely responsible for the high level of sensitisation to avian purified protein derivative (PPD), which is used for comparison purposes in tuberculosis skin testing of deer in this country. Infections with these organisms are usually subdinical in farmed deer, although M. avium subsp avium commonly causes lesions in retropharyngeal, mesenteric and ileocaecal lymph nodes. These lesions cause problems because of their gross and microscopic similarity to those due to M. bovis infection. Birds and domestic animals are most likely to become infected via environmental contamination of food, water, bedding litter or soil, while carnivores or scavengers may also become infected by ingesting infected carcasses. Johne's disease has been reported in deer in the wild and in zoos, especially in North America, the United Kingdom (UK) and Europe. Since first being confirmed in farmed deer in New Zealand in 1979, the incidence of Johne's disease has increased steadily. To date, M. paratuberculosis has been identified in >600 farmed deer on 300 properties. The majority of cases have been identified from suspected tuberculous lesions submitted from deer slaughter plants. Clinically, Johne's disease in deer is similar to the disease in sheep and cattle, with typical signs of loss of weight and condition, and diarrhoea. However, outbreaks of Johne's disease frequently occur in young red deer, 8–15 months of age, whereas the clinical disease in sheep and cattle is sporadic and usually affects adults 3–5 years of age. The disease is characterised by a chronic granulomatous enteritis and lymphadenitis, especially affecting the jejunum and ileum and the mesenteric lymph nodes. Deer affected subclinically may have lesions in these lymph nodes at slaughter, which are grossly indistinguishable from those due to bovine tuberculosis. Because of the antigenic similarity between M. intracellulare and all the subspecies of M. avium, including M. paratuberculosis, the diagnostic tests for Johne's disease lack sensitivity and specificity, making control difficult.

Nitrite inhibits hydrogen production and kills the cattle parasite Tritrichomonas foetus.

To investigate the effects of NaNO2 on the microaerophilic flagellated protozoan, Tritrichomonas foetus KV1, an economically important cattle parasite that inhabits the vagina and can spread rapidly through herds of animals by sexual transmission and leads to abortion of foetal calves. Growth of the parasite was inhibited by 50% in the presence of 4 mm NaNO2; immediate killing occurred at 10 mm. Mass spectrometric monitoring of gases showed that H2 and CO2 evolution were inhibited by NaNO2, and electron paramagnetic resonance spectrometry revealed a signal similar to that of a thiolate-iron-NO complex. Growth with sublethal concentrations of NaNO2 yielded organisms that produced ethanol rather than H2. NaNO2 probably inactivates FeS protein(s) of hydrogenosomes so as to inhibit the conversion of pyruvate (derived from maltose in the growth medium) to H2 and acetate. The use of NaNO2 as a topical antitrichomonal agent in veterinary practice is a possibility. At present, slaughter of infected animals is the favoured method of control.

Bacterial pathogens in animal feed and their control

Many tens of thousands of tonnes of manufactured feed are consumed by farm animals each year and yet the incidence of infectious diseases contracted from this source is extremely low.The potential disease hazards include, in alphabetical order, anthrax, botulism, bovine spongiform encephalopathy, foot and mouth disease, listeriosis, Newcastle disease (pigeon paramyxovirus infection), salmonellosis, swine fever and swine vesidular disease. The control of each of these diseases involves a number of different procedures, including the appropriate handling and treatment of the feed, the use of suitable management techniques on the farm, the vaccination of susceptible stock and either the treatment or slaughter of infected animals, or those animals in contact with them.Several of the diseases (foot and mouth disease, swine fever and swine vesicular disease) have been eradicated from the U.K. while others (anthrax and botulism) occur only infrequently. On the other hand, the presence of salmonellas in feed does constitute a continuing problem since, although organisms do not usually cause disease in animals consuming the feed, they may ultimately cause gastroenteritis in people who either handle or consume meat derived from the animals concerned.

Epidemiology and control of rinderpest.

Rinderpest arouses many emotions, but none more strong than the feeling of frustration born of our apparent inability to control this simple disease. We know rinderpest is principally transmitted by the movements of infected stock and that it can be curtailed by elementary zoo-sanitary measures — by the closure of markets , by the slaughter of infected animals or by quarantining infected herds. Or if politi­ cal considerations preclude these steps the virus can be eliminated by the mass application of live attenuated vaccines which give a life-long immunity. We have, then, the means of control within our grasp; yet despite this knowledge the virus persists in Africa, in India and in the Middle East. In Africa, the last five years have seen the return of rinderpest to areas from which it has been absent for a decade or more and, in the Middle East, movements of infected livestock pose a continual threat to neighbouring countries.