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Detection, Prevention and Treatment of Cattle with Trichomoniasis By Natalie Cordova Abstract Trichomoniasis is a common sexually transmitted disease that mainly affects the reproduction system of cows and bulls. It causes early abortions, infertility and even pyometra in many cows which causes an economical decrease for many ranchers. There are methods of detecting this disease even though symptoms are not blatantly present. These methods include the use of culturing DNA from the bulls and the use of PCR to efficiently diagnose the culture. Methods of preventing the disease from spreading include the culling of cows who tested positive for trichomoniasis. There are some forms of treatments currently being developed that will help eliminate the virus after it is diagnosed. One of the main forms of treatment being developed is the use of a vaccine with T. foetus antigens that will eliminate the parasite. This has been tested and has worked effectively on 37 out of 48 bulls in a study. While these treatments seem to be effective and efficient, this does raise questions on whether or not the vaccination will have any side effects on the cows and if those side effects transfer over to their production of dairy and beef. While there are some unknowns and some questions raised, there is still a strong possibility that trichomoniasis can be decreased in the future and no longer be an endemic in the United States. This can be done by completely eradicating the parasite through the use of artificial insemination as the main form of mating between bulls and cows. Literature Review While many believe there are only the main STDs known as chlamydia, gonorrhea, herpes, hepatitis, HIV/AIDS, syphilis, etc. many are not aware of one big STD known as trichomoniasis. Trichomoniasis is a common sexually transmitted infection that can happen in many organisms. It is a curable disease but still produces many problems for those infected and is caused by a parasite. This parasite is known as Trichomonas vaginalis and it is best known as a protozoan that infects humans (Burgess & Schwebke, 2004). While it is seen to affect humans, the focus of this paper will be on cattle who suffer from trichomoniasis and whether or not it can be detected early on, prevented and treated. Trichomoniasis in cattle is seen to affect these animals by a great deal. It is caused by a different protozoan known as Tritrichomonas foetus which can infect human beings as well (Yao, 2013). This parasite causes many problems in cattle, regarding their reproductive system. Reproductive systems tend to be very problematic, especially in cattle, since producing calves and providing milk are one of the main uses of cattle. Trichomoniasis in cattle is connected with early to mid-pregnancy losses, low calf rates and pyometra, which is an infection located in the uterus (BonDurant, 1997). There have been studies on these losses in cattle affected with trichomoniasis compared with cattle who are unaffected. Studies have shown that herds who tested positive for trichomoniasis have only 64% conception rates whereas unaffected herds have shown up to 96% conception rates (Yao, 2013). These large pregnancy losses are decreasing the number of calves available and not only affects themselves, but also the profits of many farmers. An increase in trichomoniasis in cattle located in California showed an estimated loss of around $66,538 (Goodger & Skirrow, 1986). This is a substantial loss mainly because they account for loss of milk and calf production as well. Loss of both of these products is an economical burden and affects the farmers since the cows are not able to do their job properly, which is producing more calves for future use, providing dairy, and serving as beef cattle. Trichomoniasis is also very problematic even if it only affects one bull out of the entire
herd. This is because it is not very well detected early on, and Yao (2013) states that one infected bull can cause infections in up to 95% of the herd when mating is undertaken. Currently, there are not very effective, legal methods for dealing with trichomoniasis. These methods are simply culling the cattle, which is known to be the most cost-effective, and quarantine of the cattle until they are culled (Michi et. al, 2016). This can prove to be a problem, and one way that can help this immensely is through early detection of this terrible infection. By detecting trichomoniasis in cattle early-on the spread of this disease can stop and can also stop the loss of income in farmers by a large amount. Before learning to detect trichomoniasis, one must first know how the protozoan comes into contact with the cattle and how it affects them. As mentioned above, trichomoniasis is caused by a protozoan called Tritrichomonas foetus and it is usually sexually transmitted between bulls and cows, but according to Felleisen (1999), it can also be transmitted through artificial insemination using contaminated fluid. After it is transmitted, it reacts differently depending on whether the female cow, or the bull is carrying the agent. If the bull contains the infection, hardly any symptoms are present whereas in the female cows, the parasites invade the vagina, uterus, and oviduct (Felleisen, 1999). While it seems to invade a large part of the cow’s reproductive system, evidence suggests it does not affect the bull by much. Bulls who are infected with the parasite do not seem to undergo problems on their fertility mainly due to the parasite not residing in the bull’s urethra (Michi et. al, 2016). While bulls do not seem to contain symptoms or many problems, they are carriers and this is dangerous considering they can easily pass the infection onto cows without one’s knowledge. Trichomoniasis also tends to infect bulls as age increases, mainly due to deeper glands forming in the reproductive system of the bulls which attracts the T. foetus parasite (Yule et. al, 1989). With parasites invading most of the reproductive system, there can be many cases of abortion, or even infertility in the female cattle. This kind of infertility is what needs to be stopped by help of detection of this infection. Currently, trichomoniasis is detected through identification of the T. foetus protozoans using data collected from the cervix of female cattle or penis of the bull (Ho, et al. 1994). This method of diagnosis is a bit ineffective as it is hard to identify small amounts of the protozoan and one might have to wait a while before they can be properly identified. With the help of more sensitive methods of detection, the accuracy of diagnosing these cattle can increase thus treating this disease at a quicker pace. One helpful method that can increase the sensitivity is the use of a DNA probe that is very aware of the T. foetus virus and can easily detect it. This method has been tested by Ho, et al (1994) and has resulted in being a more effective method than simply observing the protozoans microscopically. Another method that has proven to be more efficient and reliable is the use of PCR to amplify T. foetus DNA. The use of PCR to diagnose the T. foetus culture has shown to be very effective with a sensitivity reading of around 66% and a specificity reading of greater than 90% (Michi et. al, 2016). This method has also been tested by others and proved to be a great method as well. Ho et. al (1994) also tested this method and found it easier to perform, more accommodating, and very quick and efficient. By being more accommodating, this simply means that more samples can be used at once and therefore, a larger number of cattle can be diagnosed and treated right away. Another way to provide more accurate results would be including cell culture along with the use of the PCR to detect the T. foetus. This has provided much more accurate results as cell culture provides a sensitivity reading that ranges from 84% to 96% depending on the conditions (Michi et. al, 2016). This is one of the best and most efficient ways to prevent trichomoniasis in cattle after it has already infected the herd and can put a stop towards the spread of the parasite.
Ethical Issues While these vaccines have proved to be very effective in preventing and even eliminating infections in the cattle, it is not yet a legal or standardized treatment in any part of the world (Michi et. al, 2016). This is a problem for many farmers as without these important new treatments, there are hardly any other viable options for cattle with trichomoniasis. One of the only forms of controlling the spread of the disease is through culling of the cattle and quarantine of the cattle until they are sent for slaughter (Michi et. al, 2016). Also the option of vaccinations has been known to raise ethical questions as to the effects of these vaccines on the cows. This can also raise the question on whether or not the vaccination is ethically safe in regards to human consumption of beef and dairy. Not only are the vaccines new and recently developed, there are instances where it has not worked on some bulls. In a study reported by Michi et. al (2016), most vaccinations worked on younger bulls while 11 out of 48 vaccinated bulls still contained the T. foetus parasite. This means the vaccine still has a long way to go considering it has not provided a very high probability of eliminating the parasite. Along with fear of uncertainty in the effectiveness of the vaccine, there is also fear of the side effects the vaccine will have on these cattle regarding human consumption and cattle conception. Since vaccination only reduces the time the parasite is in the cattle, it prevents abortion but it does not prevent the natural occurrence of trichomoniasis (Fuchs et. al, 2017). This means the vaccine cannot prevent trichomoniasis from arising once again in the cattle which raises the question on whether or not it can be detected in time, especially for dairy and beef cattle. There is concern over whether there is enough time to detect trichomoniasis in cattle who are sent for purposes of human consumption. Also questions on the vaccinations remain as well, wondering if these vaccinations not only effectively prevent trichomoniasis but also do not cause side effects and problems in humans. This concern stems from studies showing other vaccinations producing harmful effects on their host. Many people simply do not want to be consuming vaccinated dairy or meat products if it produces a side effect on the cattle itself. Some of these ethical concerns should be addressed specifically and are helpful towards providing a safer and more effective treatment option for these cattle. Future Directions While trichomoniasis is considered an endemic in the United States and has been around for a substantial amount of time, there are still many things that remain unknown about this disease. One of the unknown areas in this disease is the side effects the vaccine produces and how it can be improved. This has been questioned considering data from Michi et. al (2016) that suggests that the vaccines work better with younger bulls. This type of information can be put forward into more research that can improve the vaccination and pertain it to all cattle in order to prevent this disease from spreading. While it is also known how trichomoniasis is contracted, as stated above by Felleisen (1999), it is unknown how it can be contracted through a natural occurrence. These areas of study are something that should be further looked into in order to effectively understand the T. foetus parasite. Even though some areas of study remain a bit uncertain and in the dark, there are forms that can solve these ethical issues some trichomoniasis treatments propose. Due to concern over trichomoniasis re-emerging after being treated once, this can be solved with a change of policies that require constant screening for the T. foetus parasite in order to detect if the animal contracted the disease once more. Currently there are only state regulations put into place to reduce the disease and minimize the money lost (Yao, 2013). These state regulations include regulations
that require bull testing and are very helpful if implemented nationally, and even globally. One thing that these state regulations contain is that they do not allow bulls who test positive for trichomoniasis to be imported and are culled (Yao, 2013). This is an efficient way to prevent the spread of trichomoniasis to dairy and beef cattle. Another reasonable conclusion towards the problem proposed on the vaccinations is a simple conclusion. This vaccination is not yet legal and has only been tested recently (Michi et. al, 2016). Since it is not yet legal, there is room for more development in this experiment as well as more trials to ensure the vaccination developed becomes more effective and accurate in reducing and eliminating this disease as well as removal of any possible side effects produced. These solutions are simple, efficient and logical in preventing trichomoniasis. With all this information coming to light as well as the need for information in certain areas of this study, there are also possible areas for improvement. These kinds of improvements include a vaccine developed that can prevent trichomoniasis altogether. Currently, there are only vaccines that get rid of the T. foetus virus after it has been diagnosed and there is still a possibility for contraction of the infection after the vaccine has been distributed. One way to prevent the contraction of this disease altogether, is the development of a vaccine to counteract the parasite before it manages to develop and colonize in the cattle’s body. This type of vaccine can prevent this infection from spreading and even finding its way inside the reproductive system of these cattle. Perhaps further research can develop this possibility into something that can eradicate this disease altogether. As mentioned above, there can be further steps implemented to completely eradicate this disease. While better methods of detection and treatment are helpful in the prevention of this infection, one way to stop this spread is by preventing the disease from spreading altogether. This method of eradication is through the use of switching only to artificial insemination in cattle. Artificial insemination has been used widely throughout Europe, and as a result, Europe has eradicated this disease from cattle (Yao, 2013). If the United States would widely adopt artificial insemination as the main form of reproduction, trichomoniasis has a possibility of becoming completely eradicated and no longer considered an endemic. Trichomoniasis is known as a common and, sometimes, fatal disease. By using these means of prevention, detection, and treatment these disease rates could decrease substantially and possibly even become eradicated. Literature Cited Edmondson, M., Joiner, K., Spencer, J., Riddell, K., Rodning, S., Gard, J., and Givens, D. 2017. Impact of a killed Tritrichomonas foetus vaccine on clearance of the organism and subsequent fertility of heifers following experimental inoculation. Theriogenology. 90: doi: 10.1016/j.theriogenology.2016.09. Felleisen, R. 1999. Host-parasite interaction in bovine infection with Tritrichomonas foetus. Institute of Parasitology, University of Bern, Länggass-Str. 1:10 doi: http://dx.doi.org/10.1016/S1286-4579(99)80083- Fuchs, L., Fort, M., Cano, D., Bonetti, C., Giménez, H., Vásquez, Bacigalupe, D., Breccia, J., Campero, C., and Oyhenart, J. 2017. Clearance of Tritrichomonas foetus in experimentally infected heifers protected with vaccines based on killed- t. foetus with different adjuvants. Instituto Nacional de Tecnología Agropecuaria. 35:9 doi: http://dx.doi.org/10.1016/j.vaccine.2016.12.
