Center for Food Animal Health

Agricultural Issues

Cattle Care Standards: Recommendations for Meeting California Legal Requirements

Cattle Care Standards with respect to California animal cruelty statues have been established to educate animal control officers when interpreting and applying statues.

Please see Cattle Care Standards: Recommendations for Meeting California Legal Requirements (pdf) which provides expert opinions of the authors regarding minimum standards of Cattle Care. This publication should not be considered official California regulatory agency guidance. Neither the authors nor the University of California has the authority to adopt regulations of general application.

Emerging Animal Diseases

A study was conducted that focused on two potential emerging diseases, foot and mouth disease and bovine spongiform encephalopathy (BSE). Both of these diseases could have a devastating impact on California and the U.S. agriculture. The foot and mouth diseases study initially focused on the economic impact of the disease to California's economy. The estimated economic impact was $6 billion or possibly as much as $13 billion. These figures are the latest projections of any government agency and have been used by government and media reporters to quote the economic impact of FMD on California. The BSE study focused on the impact of the disease on livestock production and the potential losses associated with the disease should it show up in California. The studies on both diseases have raised the awareness of the impact of these diseases on California animal production systems.

Trichomoniasis

Trichomoniasis is a parasitic disease of the reproductive tract of cattle caused by Tritrichomonas foetus. The disease is manifested in cows that fail to conceive, abort fetuses or have prolonged calving intervals. The protozoal organisms are most readily transmitted in nature by bulls from cow to cow. This is further complicated by cattle on the range that may be bred by bulls from other herds thereby spreading infection widely. The infection in a bull is usually mild or unapparent. The infection may persist in cows so that subsequent breedings are associated with failed conceptions. These are costly to cattleman as they are dependent on cows producing calves annually for business profits. In the case of dairy cattle, failure to conceive will lead to losses in milk production with a subsequent loss of income. Trichomoniasis has been recognized as one of the top economic diseases by beef cattle producers in California and the other Western states. Efforts to control infection in herds has been associated with purchasing and using breeding bulls free of infection, vaccinating cattle and bulls, and lastly attempting treatment. Ideally, the best strategy is to have herds free of infection and to maintain the herds as disease free. This is very difficult with range cattle. Vaccines are equivocal as they are sometimes reasonably effective in cows, but less effective in bulls. Treatment is costly and very difficult to do with range cattle.

Issue

  • Develop improved diagnostic technology to facilitate testing for excluding the infections from herds.
  • Develop a better understanding of the immune response necessary for protective immunity and improved vaccines.

Research Findings
During the research efforts to develop improved diagnostic technology, a new Trichomonad was identified. This new agent does not appear to cause disease, however it has lead to false diagnosis by many laboratories. Efforts are underway to develop reagents that will differentiate this newly recognized trichomonad from the T. foetus. Relative to evaluation of the immune response to T. foetus, the studies indicated that T. foetus is able to escape detection of the immune system or to use the antibodies of the immune system to protect it against destruction by the cow. These factors are being further studied so that a different form of protective immunity can be developed.

Impact
Recognition of the newly recognized trichomonad and the ability to differentiate it from T. foetus is of considerable value for more effectively identifying infected carriers of infection. This facilitates separating out infected bulls from herds and certifying herds free of infection. This management approach appears to be the best approach for controlling infection at this time.

Cryptosporidiosis

Cryptosproridiosis is an important parasitic disease of animals and humans. It is one of the over 350 zoonotic diseases that affects both animals and humans. The protozoal parasite is most often transmitted through contaminated water, but it can be transmitted by oral/fecal contact or contaminated foods. The parasite localizes in the intestines where it causes a severe diarrhea. Infection of immunocompromised individuals such as the aged, young, or those with AIDS or on cancer chemotherapy are at risk and may die from the infection. Some of the most explosive outbreaks of disease reported in the U.S. have been associated with cryptosporidiosis. An outbreak of the disease in Milwaukee, Wisconsin affected 400,000 people. The water supply had been contaminated and the Center of Disease Control and Prevention epidemiologists indicated that the source of the infectious agent was dairy cattle wastewater runoff. The disease occurs throughout the U.S. each year and livestock are thought to be the source of infection. The usual chemical for destroying bacterial contaminates in water supplies, chlorine, is not effective for killing the cryptosporidial parasites. In California, many water districts that maintain reservoirs to hold surface water for domestic water supplies, proposed fencing out cattle and horses from range lands on the reservoir watersheds. The elimination of these grazing lands would have a major negative impact on California rangelands for both livestock production as well as the wildlife and human activities in these areas.

Issue

  • Determine whether cattle are a significant shedder of infectious organisms into the environment and surrounding water supplies and; if so,
  • Develop management guidelines that can be used to minimize the risk of cattle being a source of the agent in the immediate environment.

Research Findings
Evaluation of cattle for disseminating Cryptosporidia into the environment indicated that adult cattle rarely shed the agent. The age of greatest risk for contaminating the environment occurs within the first few weeks of life and calves are seldom in areas where watersheds would be contaminated. This is the case in Western U.S. Surprisingly, the animal with the highest rate of shedding Cryptosporidia into the environment was the ground squirrel.

Recommendations
Newborn calves should not be in areas where there is a possibility of contaminating the environment around watersheds during the first 8 weeks after birth.

Impact
These research findings have made it possible to permit cattle to graze on watersheds that are used for surface water storage for human consumption. By permitting the cattle to graze on theses lands, the cattle have reduced overgrowth of grass lands and reduced fire danger.

Bluetongue

Bluetongue is a viral disease of ruminants that is found in tropical and temperate climates of the world. There are 24 serotypes of these viruses worldwide that are transmitted by Culicoides flies. These biting flies are the principle means of determining the distribution of bluetongue worldwide. Furthermore the virus serotypes seem to be reasonably stable within an ecosystem. Bluetongue disease causes its most serious damage to sheep where the lesions lead to erosive and ulcerative lesions of the mouth, damage to muscle and cardiac muscle, and extensive lameness along with high body temperatures. Up to 30% of a flock may die from the infection. Cattle appear to be the main species that are infected; however they rarely show evidence of disease. Instead cattle have prolonged viremias permitting insects to pick up the virus over longer periods of up to 150 days following infection. There is also evidence that bluetongue viruses can be transmitted through semen to susceptible cows. Because of these findings, bluetongue is consider a List A disease by the Organization of International Epizootics (O.I.E.), and as a rest of this listing, severe trade restrictions are placed on countries that plan to export ruminants or ruminant germplasm from countries that have the bluetongue infection to other countries. Much of the information used to base the listing on is outdated and due to a failure to understand the biology of the viruses and Culicoides vectors.

Issue

  • Define the biology of bluetongue viruses, culicoides flies and the ecosystems of these viruses in different parts of the world.
  • Develop science based information for policy decisions that would permit new approaches for international trade of ruminants and ruminant germplasm.

Research Findings
Studies on cattle experimentally infected with bluetongue virus defined that they are viremic for 50 days, but no longer than this. The culicoides flies were able to pick up virus from the these infected cows for up to 30 to 45 days after infection and transmit the virus to other ruminants. In studies comparing bluetongue viruses from China with those from the U.S., it was clear from genetic analysis of the viruses that the serotype distribution between the countries was different but the major factor defining the distribution of the viruses was the selected gene segment favoring the culicoides in their respective ecosystems.

Impact
New regulatory information has been drafted for consideration by the 125 member countries of the O.I.E. based on the scientific information derived from the above research. The basis of the information clearly demonstrated that cattle carry the infected virus for up to 50 days following infection, rather than 150 days and that the amount (titer) of virus in blood that culicoides flies can pick up is seldom more that 30 to 45 days. This information can now be used to hold animals for considerably less time in quarantine before shipment to foreign countries. Also, the information about the confinement of bluetongue to different ecosystems based on the genetic predisposition of the viruses to the particular culicoides flies of that region/ecosystem will make a major difference in understanding the distribution of these viruses in the world. This will eventually lead to eased trade restrictions.