Disease Eradication Programs Research Articles

Globalization of Communicable Animal Diseases – A Crisis of Veterinary Medicine

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What's hot in animal biosafety?

In recent years, the emergence or re-emergence of critical issues in infectious disease and public health has presented new challenges and opportunities for laboratory animal care professionals. The re-emergence of bioterrorism as a threat activity of individuals or small groups has caused a heightened awareness of biosecurity and improved biosafety. The need for animal work involving high-risk or high-consequence pathogens and for arthropod-borne diseases has stimulated renewed interest in animal biosafety matters, particularly for work in containment. Application of these principles to animals retained in outdoor environments has been a consequence of disease eradication programs. The anticipated global eradication of wild poliovirus has prompted the promulgation of new biosafety guidelines for future laboratory and animal work. Increased concern regarding the use of biologically derived toxins and hazardous chemicals has stimulated a new categorization of facility containment based on risk assessment. Recognition that prion disease agents and other high-consequence pathogens require safe handling and thorough destruction during terminal decontamination treatment has led to the development of new biosafety guidelines and technologies. The implementation of these guidelines and technologies will promote state-of-the-art research while minimizing risk to laboratory animals, researchers, and the environment.

Brucella vaccines in wildlife

Brucellosis has been known to exist in populations of wildlife since the early part of the 20th century. At the beginning of this century in the US, Brucella abortus is a problem in elk and bison in the Greater Yellowstone Area, B. suis is prevalent in millions of feral swine in most of the southern states, and caribou/reindeer in Alaska are infected with B. suis biovar 4. Brucellosis has been virtually eliminated in domestic livestock in the US after decades of expensive governmental disease prevention, control and eradication programs. Now the most likely source of transmission of brucellosis to humans, and the risk of reintroduction of brucellosis into livestock is from infected populations of free-ranging wildlife. Brucellosis was eradicated from livestock through a combination of testing, vaccination, and removal of infected animals. The use of vaccines to control brucellosis in populations of wildlife and therefore reducing the risk of transmission to humans and livestock has been proposed in several instances. This manuscript reviews research on the use of Brucella vaccines in species of wildlife with emphasis on safety and efficacy.

History and prospects for viral disease eradication.

Edward Jenner first articulated the concept of eradication when he first inoculated the vaccinia. Before considering a disease for eradication some factors should be considered, such as the biological characteristics of the infectious agent: does the infectious agent infects only humans? Does it have a non-human reservoir and induce long-life immunity after infection? Is there a tool or intervention that effectively interrupts the chain of transmission from one individual to another? The first disease to be eradicated was smallpox. This extraordinary initiative set the example for any future disease eradication program. The eradication of polio from the Americas was launched in May 1985 and the Region of the Americas was certified polio-free in September 1994. At this same year, the Pan American Health Organization (PAHO) launched an initiative to eradicate measles from the Americas. Only 1,500 cases have been reported during the year 2000, and transmission was interrupted in most countries of the Region. Tremendous progress has been achieved in disease eradication efforts, which resulted in the global eradication of smallpox, the eradication of poliomyelitis from the Americas and its nearly global eradication, and the nearly complete eradication of measles from the Americas. The biotechnology revolution is providing us with many new vaccines and we have to continue the search for those diseases that could eventually be eradicated. Eradication of a disease brings the greatest health benefit, which is the absence of the health threat. It is also the quintessential example of health equity, as all mankind reaps the benefits, bringing eternal cost savings. As Louis Pasteur pointed out, "it is within the power of man to eradicate infection from the earth".

Dracunculiasis (Guinea worm disease) and the eradication initiative.

Dracunculiasis, also known as guinea worm disease, is caused by the large female of the nematode Dracunculus medinensis, which emerges painfully and slowly from the skin, usually on the lower limbs. The disease can infect animals, and sustainable animal cycles occur in North America and Central Asia but do not act as reservoirs of human infection. The disease is endemic across the Sahel belt of Africa from Mauritania to Ethiopia, having been eliminated from Asia and some African countries. It has a significant socioeconomic impact because of the temporary disability that it causes. Dracunculiasis is exclusively caught from drinking water, usually from ponds. A campaign to eradicate the disease was launched in the 1980s and has made significant progress. The strategy of the campaign is discussed, including water supply, health education, case management, and vector control. Current issues including the integration of the campaign into primary health care and the mapping of cases by using geographic information systems are also considered. Finally, some lessons for other disease control and eradication programs are outlined.

Milk antibody testing in cattle

MILK antibody testing has played a significant role in cattle disease control and eradication programmes in many countries, particularly in mainland Europe and Scandinavia, since the mid-1980s. In Britain, bulk...

Improved antigen and nucleic acid detection in a bovine virus diarrhoea eradication program

A bovine viral diarrhoea/mucosal disease (BVD/MD) control and eradication program was introduced in Lower Austria in 1996, according to the Swedish model. An important risk factor for BVD transmission under local conditions is communal grazing where susceptible pregnant cattle from several herds may be mixed with unrecognised persistently infected (PI) animals. A reliable system for identification of PI animals is therefore essential for BVD eradication and steps were taken to improve a commercially available antigen-capture ELISA (Ag-ELISA) by modifying the method for leukocyte preparation and adjusting the negative cut-off value. A single-tube reverse transcriptase-polymerase chain reaction (RT-PCR) employing panpestivirus 324/326 primers targeting the 5′-untranslated region of the virus genome was also simplified and used on pooled blood samples to facilitate larger sample throughputs. RT-PCR positive pools were analysed individually to identify infected animals. Seven hundred eighty-six samples were tested by Ag-ELISA according to the instruction manual and 5324 samples with the modified method. All 6110 samples were retested by RT-PCR. The percentage of RT-PCR positive results with doubtful and negative Ag-ELISA samples significantly diminished using the modified method (from 4.71 to 0.82%). Selected BVD viruses were genetically typed by PCR product sequencing; special attention being paid to RT-PCR amplicons from samples which were negative or doubtful by ELISA. However, no correlation was found between the phylogenetic grouping of the viruses and the Ag-ELISA results.

Epidemiological concepts regarding disease monitoring and surveillance.

Definitions of epidemiological concepts regarding disease monitoring and surveillance can be found in textbooks on veterinary epidemiology. This paper gives a review of how the concepts: monitoring, surveillance, and disease control strategies are defined. Monitoring and surveillance systems (MO&SS) involve measurements of disease occurrence, and the design of the monitoring determines which types of disease occurrence measures can be applied. However, the knowledge of the performance of diagnostic tests (sensitivity and specificity) is essential to estimate the true occurrence of the disease. The terms, disease control programme (DCP) or disease eradication programme (DEP), are defined, and the steps of DCP/DEP are described to illustrate that they are a process rather than a static MO&SS.

An international approach to laboratory diagnosis of animal diseases.

During the past thirteen years, and as part of an overall support program for developing countries, the Joint FAO/IAEA Division has developed a series of standardized and internationally validated ELISA-based systems for the diagnosis and surveillance of the major epizootics affecting livestock in the developing world. Linked to comprehensive internal and external quality assurance protocols and to the use of standardized equipment and data management software, veterinary laboratories in many developing countries are now able to provide quality assured results on the prevalence of the major diseases affecting their livestock. This internationally standardized approach can rapidly enable developing countries to both monitor the effectiveness of their disease control and eradication programs and to meet requirements for international disease status recognition and for trade in livestock and livestock products.

Effect of pasteurization at 76 and 63 degrees C on the absorption of colostral IgG in calves.

The timely ingestion and absorption of colostral immunoglobulin is a critical determinant of neonatal calf health. Calves are born without appreciable concentrations of the serum immunoglobulins needed to protect against pathogenic bacteria, viruses and protozoa (Tyler & Parish, 1995). The beneficial effect of passive transfer of colostral immunoglobulin also extends beyond the neonatal period and persists into juvenile and adult life (Robison et al. 1988; Tyler et al. 1998; DeNise et al. 1989). Calves with failure of passive transfer, defined as serum protein < 50 g/l or serum IgG < 10 g/l, have increased mortality risks that persist until 10 weeks of age (Tyler et al. 1998).Several diseases are potentially spread by the ingestion of colostrum, including bovine leukosis and Johne's disease (Perrin & Polack, 1988; Streeter et al. 1995). In one study 22% of latently infected cows were demonstrated to shed Mycobacterium paratuberculosis in their colostrum (Streeter et al. 1995). Optimal programmes to prevent and eradicate these diseases generally include the provision that calves are given colostrum derived from cows of known negative disease status. Pasteurization or heat treatment of colostrum may provide a mechanism whereby calves are provided with protection against neonatal disease without creating undue potential for infection by chronic, economically relevant diseases.Attempts to heat disinfect colostrum are common in goat herds (MacKenzie et al. 1987). Pasteurization has been demonstrated to be effective against the caprine arthritis–encephalomyelitis virus (Adams et al. 1983; MacKenzie et al. 1987). Although Myco. paratuberculosis appears to resist pasteurization, this form of processing has been demonstrated to decrease the likelihood of positive colostral cultures for Myco. paratuberculosis under experimental conditions (Meylan et al. 1996). Sterilizing the milk and colostrum given to calves is a logical and reasonable strategy to prevent transmission of infectious microorganisms. The potential disadvantage of heat treating colostrum is that the immunoglobulins in colostrum may become denatured (Smith & Sherman, 1994). Pasteurization causes only a slight decrease in the colostral concentration of IgG in cattle (Meylan et al. 1996); however, the biological behaviour of these pasteurized immunoglobulins has not been critically examined. Therefore, we cannot be completely confident that immunoglobulin absorption, persistence in serum and biological activity are unchanged by this processing.The goal of this study was to determine the effect of pasteurization at 76 and 63 °C on the absorption of IgG from colostrum. Should these procedures decrease immunoglobulin absorption, the use of pasteurization in disease eradication programmes would require increased efforts to optimize the passive transfer of immunoglobulin.

When is a disease eradicable? 100 years of lessons learned.

Since the 1915 launch of the first international eradication initiative targeting a human pathogen, much has been learned about the determinants of eradicability of an organism. The authors outline the first 4 eradication efforts, summarizing the lessons learned in terms of the 3 types of criteria for disease eradication programs: (1) biological and technical feasibility, (2) costs and benefits, and (3) societal and political considerations.

A multiplex approach to molecular detection of Brucella abortus and/or Mycobacterium bovis infection in cattle.

A multiplex amplification and detection platform for the diagnosis of Mycobacterium bovis and Brucella abortus infection simultaneously in bovine milk and nasal secretions was developed. This system (designated the bovine pathogen detection assay [BPDA]-PCR) consists of duplex amplification of species-specific targets (a region of the BCSP31K gene of B. abortus and a repeat-sequence region in the hsp65 gene of M. bovis, respectively). This is followed by a solid-phase probe capture hybridization of amplicons for detection. On the basis of spiking experiments with normal milk, the analytical sensitivity of the assay was 800 CFU equivalents/ml of milk for B. abortus and as low as 4 CFU equivalents per ml of milk for M. bovis. BPDA-PCR was validated with 45 liver samples from lemmings experimentally infected with B. abortus. The assay sensitivity, based on culture status as a "gold standard," was 93.9%. In this experiment, BPDA-PCR also identified five culture-negative liver samples as positive (41.7%). Field studies for the evaluation of BPDA-PCR were performed with samples from dairy animals from geographically distinct regions (India, Mexico, and Argentina). A high prevalence of shedding of B. abortus (samples from India) and M. bovis (samples from Mexico) was identified by BPDA-PCR. In samples from India, B. abortus shedding was identified in 86% of milk ring test-positive animals (n = 15) and 80% of milk ring test-negative cows (n = 5). In samples from Mexico, M. bovis was identified by PCR in 32.6% of pools (n = 46) of milk that each contained milk from 10 animals and in 56.2% of nasal swabs (n = 121) from cattle from tuberculin test-positive herds. In contrast, the Argentine cattle (n = 70) had a modest prevalence of M. bovis shedding in nasal swabs (2.9%) and milk (1.4%) and of B. abortus in milk (11.4%). On the basis of these analyses, we identify BPDA-PCR as an optimal tool for both screening of herds and testing of individual animals in a disease eradication program. A combination of the duplex assay, screening of milk samples in pools, and the proposed algorithm provides a highly sensitive, cost-effective, and economically viable alternative to serological testing.

Procedurally similar competitive immunoassay systems for the serodiagnosis of Babesia equi, Babesia caballi, Trypanosoma equiperdum, and Burkholderia mallei infection in horses.

Procedurally similar competitive enzyme-linked immunoassay (cELISA) methods were developed for the serodiagnosis of Babesia equi and Babesia caballi (piroplasmosis), Trypanosoma equiperdum (dourine), and Burkholderia mallei (glanders) infections in horses. Apparent test specificities for the B. equi, B. caballi, T. equiperdum, and B. mallei cELISAs were 99.2%, 99.5%, 98.9%, and 98.9%, respectively. Concordances and kappa values between the complement fixation (CF) and the cELISA procedures for the serodiagnosis of B. equi, B. caballi, T. equiperdum, and B. mallei infections in experimentally exposed horses were 76% and 0.55, 89% and 0.78, 97% and 0.95, and 70% and 0.44, respectively. The cELISA method may be a technically more reproducible, objective, and convenient approach for piroplasmosis, dourine, and glanders serodiagnosis in qualifying animals for international movement and disease eradication programs than the CF systems currently in use. Use of the cELISA method also obviated the problems associated with testing hemolyzed or anticomplementary sera.

Central or national veterinary diagnostic laboratories.

Information on laboratory organisational structure and roles was gathered from twenty-four national veterinary diagnostic laboratories around the world. This information was used to develop an overview of the organisation and roles of the national veterinary diagnostic laboratory. In addition, the national diagnostic laboratory for the United States of America (the National Veterinary Services Laboratories) was used as an example to provide more information on the activities of such a laboratory. The survey revealed great variation in organisation and structure among the twenty-four laboratories. A few have only one facility, others function at multiple locations, and all have different supervisory reporting systems. However, these laboratories all form a significant part of the national veterinary infrastructure. All of the laboratories contacted in the survey report to (or are at least partially under the direction of) the Chief Veterinary Officer or another senior animal health official, and most report to the Ministry of Agriculture. The national veterinary diagnostic laboratories have similar roles, and are all responsible for foreign animal disease diagnosis and for providing support to national disease eradication or control programmes. Most also play an active role in import and export testing, either performing the tests themselves or developing a quality assurance programme for other laboratories that perform the testing. In addition, the national veterinary diagnostic laboratories usually undertake research and provide training, consultation, disease surveillance information and, in some cases, vaccine evaluation.

Eradication and control programmes against Aujeszky's disease (pseudorabies) in France

In the present paper, an overview is given about the Aujeszky's disease (AD) eradication programmes currently applied in the different departments of France, together with the obtained results.

Risks and economic consequences of introducing classical swine fever into The Netherlands by feeding swill to swine.

An effective animal disease prevention and eradication programme is of great importance for meat-exporting countries such as the Netherlands. If a serious outbreak of disease were to occur, the eradication measures required by the European Union and a possible ban on meat exports would have severe economic consequences. However, historical and experimental information on which these programmes can be based is scarce. Furthermore, until recently, an integrated approach which combined the various aspects of outbreaks and risks with economic consequences was lacking. This paper describes a project based on such an integrated approach. The project covered the elicitation of expert knowledge and the development of the virus introduction risk simulation model (VIRiS). VIRiS integrates objective and subjective information concerning risks and consequences of virus introduction, and thus presents policy-makers with a useful tool for the evaluation of existing prevention programmes and possible alternatives. VIRiS is illustrated for classical swine fever. A comparison is made between the current situation and a hypothetical situation where the risk factor 'swill feeding' is completely eliminated.

JOhne's Disease Eradication and Control: Regulatory Implications

The time has come for the livestock industry and the veterinary profession to take Johne's disease seriously in the United States. The continued spread of the disease with accompanying economic hardship to infected herds and the possibility that M. paratuberculosis may be a food-borne pathogen makes inaction a costly proposition. Efforts have started at the national level with NJWG to have guidelines written for a national control program for Johne's disease. A national control program is desirable because it would provide uniformity to control efforts. Veterinarians and livestock owners should be aware of the effort and let their views be known. In addition, national program guidelines already have been written (see the appendix) to certify test-negative herds for paratuberculosis. States that do not offer the certification program should consider it. A list of test-negative herds for Johne's disease that livestock owners could use to buy low risk animals would be a significant step forward in our efforts to control Johne's disease. Federal regulations concerning Johne's disease are outdated and should be changed to facilitate participation by the livestock industry in a Johne's disease control and eradication program.

The Yoruba farm market as a communication channel in guinea worm disease surveillance

Disease eradication programmes are by definition time bound and require strategies that facilitate timely intervention. Surveillance, which undergirds eradication, also requires timely strategies. Finding such strategies is especially challenging when the target disease is endemic in remote areas, e.g. guinea worm disease, the focus of this study. A strategy of market based surveillance was pilot tested in Ifeloju Local Government Area (LGA) of Oyo State, Nigeria. The project gaol was to design a surveillance system that both fit into the natural communication network of rural people, and also enlisted their active involvement. Ethnographic research methods were employed to learn about market location, structure, catchment area and attendance pattern. Four larger farm markets (serving 164 hamlets with 17,000 population) were chosen. Each hamlet was visited and a volunteer ‘reporter’ was recruited. Reporters were trained on case recognition and detection, first aid and prevention, with a sensitivity to distinguishing indigenous and clinical perceptions of guinea worm. The market cycle was based on the traditional four-day week. Field workers visited every second market 16 times between October 1990 and February 1991. The reporter was expected to identify correctly the first case of the season and thus label the village as endemic for the season. Reporters gave oral reports, and positive indications were followed up within 48 hr by field workers, who verified the case and administered first aid. All hamlets were visited once a month to verify negative reports. Reporter attendance was monitored. Those who had a formal role in the market, e.g. sales agents, had better attendance than ordinary farmers who came only to sell their own produce. Knowledge of market structure and attender roles offers a guide for adapting this surveillance approach to other cultural systems and health issues.

Pseudorabies (Aujeszky's disease) eradication progress and program costs in Ohio, USA

The purpose of this study was to document how the Ohio pseudorabies (PRV) (Aujeszky's disease) eradication program has progressed to its current status from its initiation in 1977 to the present, as well as to project the year and program costs of eradication of PRV from Ohio, based on a retrospective study of data retrieved from records available on swine herds quarantined in Ohio. All swine herds newly quarantined for PRV from January 1985 to 31 December 1992 ( n = 446) were eligible for the study, 374 (84%) of which had useable data available. Projected year of PRV eradication from Ohio was 1996. Information on detection methods of newly infected herds were only available for 52 of the 374 (14%) data files reviewed from 1985 through 1992, with laboratory diagnosis accounting for 30 of 52 (58%). ‘Area spread’ was identified as the most likely source of PRV infection of newly quarantined herds in 140 of 194 (72%) for which data files were available from the time period 1985 to 1992. Information on herd plans used in the same time interval were available for 285 of the 374 data files (76%). The median number of months under quarantine per herd from 1986 to 1992 were 7.7 months, 6.2 months, 5.9 months, 5.1 months, 17.3 months, 18.9 months and 12.3 months, respectively. Finally the average yearspecific cost per herd-month under quarantine representing 54% of herds released from quarantine for each of the years 1986 through 1992 ranged from $795 in 1990 to $2999 in 1992 and were based on the total amounts of money available and spent in the Ohio PRV eradication program. According to the cost analysis of the period 1993–1998, eradication of PRV can be achieved in Ohio, as projected, by 1996 at a minimum public cost of about $3.7 million discounted to 1992 dollars.

Field Evaluations and Applications of Electronic Identification (EID) Systems in the Bovine Industry

Automatic identification of members of the bovine family is very important in present and future developments of livestock production. From securing export of healthy live animals and meat with genetic superiority to automating health records and production records; automatic identification has the potential to play a significant role in the livestock industry.
 The technology evaluated is the implantable, passive, electronic identification transponders manufactured by Destron/IDI, of Boulder, Colorado. Transponders were implanted in over 4549 animals during 1991 and 1992 in the United States, Canada and England, evaluating the following:(1.) implanting technique(2.) transponder retention(3.) automation with various animal production systems(4.) carcass identification within the slaughterhouse(5.) slaughterhouse recovery of transponders(6.) disease eradication programs(7.) breed registration(8.) alternative identification to branding and other forms of identification.
 The above items will be discussed in some detail as related to the trials performed on animals.