The Potential Impact of Using Biological Weapons Against Livestock and Crops

Ryszard Koczura, Adam Kaznowski, Adam Mickiewicz
University, Institute of Experimental Biology,
Department of Microbiology, ul. Fredry 10, 61-022 Poznak, Poland
Tel: +48 61 8294529; Fax: + 48 22 8295550
E-mail: koczma@amu.edu.pl

Introduction

          Terms such as “bioterrorism” or “biological warfare” are usually related to humans as the target; however, there is a rising concern that agriculture may also become a target for terrorist using biological agents.
          The use of biological weapon for sabotage against livestock and crops, also called agroterrorism, could have severe consequences for food industry and national economy. Even a small outbreak of an infectious disease can prompt other countries to outlaw import of plant and animal material that may introduce the disease into their territory. This can result in loss of international market for the affected country and thus create very large economic effects.

History of Biological Warfare Targeting Animals

          Infectious agents and biological toxins have been used as weapons of war from ancient times. Although their use was directed primarily against human population, one should keep in mind that livestock and crops may also be targeted.
          It is worth noting that the first allegation of using biological weapon in the XX century was against livestock, not against human. During World War I, Germany used Bacillus anthracis and Burkholderia mallei against horses, mules, cattle, sheep, and reindeer in Romania, Spain, France, Norway, Argentina, and the United States. It was a carefully planned and well executed operation conducted by secret agents on three continents and it was the first national biological warfare program (13; 2).
          Before and during World War II, many experiments with various infectious agents were conducted in some Europe countries as well as in Japan and the US, but it seems that these agents were never used in the battlefield. A noteworthy program was developed in United Kingdom; it was called “Operation Vegetarian” and included stockpiling of 5 million anthrax cakes that were to be spread over pastures in Germany. The United States and Canada had a secret animal disease research program conducted on Grossle Isle in the St. Lawrence River. The major aim of this program was to prepare a tissue vaccine against rinderpest. This research was successful in developing a vaccine grown in chicken eggs. After the World War II, the United States tested hog cholera and Newcastle disease viruses.Experimental bombs contained the viruses mixed with feathers and were to explode at a certain altitude, to allow the feathers to float down into farms. The US offensive biological weapons ended in 1969. Japanese biological warfare program, which was set up shortly before World War II, also included research on aerosol dispersion of a number of pathogens that would infect both human and animals (13; 2).
          In 1952, Mau Mau revolutionists in then-British colonial Kenya used a toxin derived from African milk bush to poison cattle. Reportedly, 33 heads were killed (1). During the war of independence in Rhodesia (now Zimbabwe) in late 1970s, there was large anthrax epidemic that affected both cattle and human. Before the war, anthrax cases in Rhodesia were rare and controlled. During the war, it became a major disease in cattle with thousands of cases and deaths. There was also a corresponding epidemic in human with about 10,000 of cases and hundreds of deaths. The introduction of anthrax was very likely intentional, to weaken the food supply of those who fought for independence (13).
          The biological warfare program of the former Soviet Union also included research on weaponizing antilivestock agents like foot-and-mouth disease virus, rinderpest virus, classical swine fever and African swine fever viruses, together with anticrop agents like wheat rust, rice blast, karnal bunt, and Fusarium spp. The Soviet antilivestock and anticrop program in its peak employed 10,000 staff. The Soviet military allegedly used B. mallei against Mujahedines in Afghanistan (13; 10).
          The most recent case of using biological weapon against animals took place in New Zealand in 1997. The local farmers acquired rabbit hemorrhagic disease virus from foreign country. The source of the virus were tissues of infected animals, smuggled into New Zealand in mail, and by air travelers. The operation required simple procedure; the infected material was blended, mixed with vegetables and distributed around farms (13).

Anti-livestock Biological Warfare Agents

          A potential antilivestock agent should have the following features: (i) highly infectious and contagious, pathogenic for livestock, (ii) easy to acquire or produce, (iii) good ability to survive in the environment, (iv) attributable to a natural outbreak, (v) not harmful to perpetrator, ad (vi) easily disseminated (13). Diseases caused by agents that fulfill the above criteria can be found on lists A and B introduced by the Office International des Epizooties (OIE). The OIE is an intergovernmental organization created by international agreement on 25 January 1924 and signed by 28 countries. In March 2004, the OIE totaled 166 member countries, including Poland. The OIE serves world animal health organization. The main objectives of the OIE are: (i) transparency in the global animal disease and zoonosis situation, (ii) collecting, analysis and dissemination of scientific veterinary information, (iii) providing expertise and encouraging international solidarity in the control of animal diseases, (iv) publishing health standards for international trade in animals and animal products, (v) improving the legal framework and resources of national veterinary services, and (vi) providing a better guarantee of the safety of food of animal origin and promoting animal welfare through a science-based approach (9).
          The OIE develops procedures, guidelines, and share information to prevent the spread and introduction of infectious diseases of livestock and poultry. The OIE introduced a list of animal diseases, where they are categorized into two levels named List A and List B.
          List A comprises 15 transmissible diseases that have the potential for very serious and rapid spread, irrespective of national borders. They are of serious socio-economic or public health consequence and are of major importance in the international trade of animals and animal products. The diseases from List A comprises: foot-and-mouth disease, vesicular stomatitis, swine vesicular disease, rinderpest, peste des petits ruminants, contagious bovine pleuropneumonia, lumpy skin disease, Rift Valley fever, bluetongue, sheep pox and goat pox, African horse sickness, African swine fever, classical swine fever, highly pathogenic avian influenza, and Newcastle disease (9).
          List B includes over 90 transmissible diseases that are considered to be of socio-economic and/or public health importance within countries and that are significant in the international trade of animals and animal products. One could say that the List B diseases are “less important” than those from list A and therefore they do not pose as much threat on international trade. This is not always true; especially as far as bovine spongiform encephalopathy (BSE) is concerned. This disease can cause long-lasting barriers to trade meat and meat products from affected. Other examples of List B diseases are: anthrax, glanders, Q fever, rabies, brucellosis or Marek’s disease (13; 9).
          The animal pathogen list has only a few agents common with the list of antihuman bioweapons agents. Actually, the exceptions are Venezuelan equine encephalitis virus, Rift Valley fever virus, Chlamydia psittaci, and B. anthracis. This is worth noting because one could assume that the same pathogens can serve as biological weapon against both human and livestock. The list of antilivestock pathogens is based on economic trade impact and ease of transmissibility, while that of human is based on high mortality or fear (13).
          Many of the agents from List A and List B may be used as bio weapons, however the following viruses pose the greatest threat as potential antilivestock weapons: foot-and-mouth disease, classical swine, African swine, rinderpest, avian influenza, and Newcastle disease (13, 2000; 2).
          Foot-and-mouth disease is one of the most contagious diseases of mammals. It affects cloven-hoofed animals. The primary mode of spread is through respiratory aerosols. The disease can be introduced by direct or indirect contact with other animals, contaminated objects (e.g. footwear, clothes fodder), or artificial insemination. It spreads very rapidly in pigs, but may not be diagnosed quickly when sheep are infected.
          Classical swine fever (hog cholera) is a highly contagious disease of swine. Pigs that are the natural reservoir of the virus. It is transmissed mostly by oral route and can be introduced into herd by an infected animal.
          African swine fever affects domestic and wild pigs. The disease occurs in several African countries and on Sardinia. It is tickborne; soft ticks Ornithodoros sp. are vectors of the virus. African swine fever can by introduced into a farm by fodder containing the virus.
          Rinderpest is a disease with high mortality. It affects cattle, sheep, and some breeds of pigs. Rinderpest spreads by contact with infected animals, but also can be transmitted by contaminated fodder or water.
          Avian influenza (fowl plague) affects poultry and a wide range of other bird species. Wild birds can be the reservoir of the virus. It spreads by contact with other birds (mostly fecal-to-oral). Note that humans can be infected as well.
          Newcastle disease, especially velogenic form, is a highly contagious disease of poultry. It affects poultry. Exotic birds may be carrier of the virus. The disease spreads by contact with other birds and contaminated objects. Newcastle disease is endemic in many countries of Africa and Asia (3).

Anti-crop Biological Warfare Agents

          Biological agents can be used also against crops, although their use by terrorists seems to be less plausible, because their use requires more effort and technology than in case of anti-animal agents. For example, in case of fungal pathogens, the spores must be obtained, stockpiled, and then disseminated under favorable weather conditions. On the other hand, relatively long period between introduction of the pathogen and discovery of the disease makes the attack difficult to realize.
          The pathogens that most likely can be used against crops are Puccinia graminis, Piricularia orizae, and Phytophthora infestans. They cause wheat rust, rise blast, and late blight of potatoes, respectively. Their ability to cause epidemics depends on several factors. The susceptibility of the host plant is essential. The epidemic in crops is also dependent upon weather conditions, like temperature, humidity or wind direction. Human activity can either facilitate or prevent the outbreak of the disease in crops. If modern crop protection practices (use of resistant varieties, crop rotation, etc.) are employed, the possibility of disease outbreak is lessened. However, when these practices are not used, the possibility of significant losses in crops is high (12).
          Experiments on the use of plant pathogens were conducted in several countries, including Germany, Japan, UK, former Soviet Union, and the US. Several fungal pathogens were evaluated. Investigations were also conducted on wheat and barley mosaic streak viruses, potato virus, tobacco mosaic virus, brown grass mosaic virus for use against barley, maize, and thorn apple. Some species of pests were also regarded as possible anti-crop agents (12; 6; 8).

Motives for Agroterrorist Attack

          There can be various motives for perpetrators using biological weapons against agriculture: political, religious, ethnic, criminal, or even opposition to the use of genetically modified food. A bioterrorist attack may be performed by terrorist groups, organized crime groups, military groups or cult sects (7; 11).
          Agriculture is an easy target for a bioterrorist event, mainly because such an attack requires little knowledge and technology. Agents for use against animals and crops can be obtained from natural sources. Majority of antilivestock and anticrop agents are not infectious to human, so they pose little or no threat to the perpetrator and can be transported on the person’s body. There is also lack of on-farm security - agricultural resources are large, exposed and unprotected, which makes them vulnerable (13; 11).

Economic Consequences Of Agroterrorist Event

          Taiwan’s epidemic of foot-and-mouth disease illustrates how serious consequences may result from agroterrorist attack. This example also demonstrates the pace at which foot-and-mouth disease can spread in a livestock population. Taiwan’s livestock sector was deeply affected by the outbreak of foot-and-mouth disease on its huge swine farms. From the time the disease was discovered on a single farm to the time it was announced, 27 other farms were contaminated. Within a week, 717 farms were infected and within three months Taiwan was fully infected and 4 million hogs were slaughtered. The Taiwan outbreak resulted in excess of 500,000 tons of pork meat being destroyed and in an indefinite ban on Taiwan's pork exports that caused Taiwan’s gross domestic product to drop by 2%. Taiwan lost its principal export markets for pork, particularly the Japanese market. Within one week of the outbreak, swine prices dropped by 60%, about 50,000 people became unemployed and $6.9 billion was lost in export revenue. The overall losses amounted to $ 15 billion. Three years later Taiwan did not fully regain its exports markets (4; 2).
          The 2001 outbreak of the disease in Great Britain also prompted the slaughter of more than 4 millions farm animals and caused billions of dollars in losses to farmers. The outbreak also lowered domestic consumption of beef in the UK and reduced beef export. The ban imposed on British beef by European Union states had also political consequences and strained London’s relations with its major European allies (10).
          Agroterrorist attack generates three levels of costs. First, there would be direct losses resulting from containment measures and the destruction of diseased livestock. Second, compensation costs will have to be paid to farmers for destruction of their agricultural commodities and losses suffered by directly and indirectly related industries. Finally, international costs would accumulate due to protective embargoes imposed by trading partners. A successful act of agroterrorism could also undermine the domesticconfidence and support of government, because the public would question the safety of the food supply (5).

Conclusions

          It is relatively easy to attack agriculture industry using bio- weapons. Natural disease outbreaks showed how severe impact can a disease have on animals or plants, but most of all it affect economics situation in the attacked country.
          Countermeasures can be undertaken to prevent a bioterrorist attack o agriculture. These include detection of terrorist conspiracies, with identification of potential targets, perpetrators, their motivation and behavior, creation of resistance in livestock, and more thorough security on farms. When the attack happens, though, early detection of the disease and containment are most important.

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