Campylobacteriosis is a disease caused by Campylobacter species. Chicken can be a source of campylobacters. Contamination of chicken can start as early as at the farm ' possibly through the water source, contact with colonised wild animals or by living with already colonised chickens. Contamination can further occur in the slaughter house. Many of the parts which chicken come in contact with can be contaminated and so are possible source for contamination. The processes involved in the slaughterhouse (e.g. defeathering, actual slaughter of the chickens) could spread contamination ' possibly onto chickens which were not colonised when they arrived at the slaughterhouse. Transmission of the disease to humans can occur while handling live or dead chickens. Chicken meat and cross contamination with other food. Poor hygiene may account for this. Eating raw or undercooked meat also poses a risk. Coriander oils, phage treatment and thorough cooking of meat have been suggested as possible means of control.
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Campylobacteriosis is an important human disease. Campylobacters are one of the most reported causes of diarrhea in developed countries (Allos and Blaser 1995). However, the reports of infection by campylobacters may be underestimated because, unless the right conditions are met, the bacteria are difficult to keep alive in the laboratory (Skirrow 1977). Allos and Blaser (1995) also give several reasons for under reporting, including lack of symptoms or patients not seeking treatment.
Transmission between people is possible, although it happens infrequently and so is not as important as other possible infection routes (Allos and Blaser 1995).
Studies have indicated that chicken may be an important source of the bacteria which cause this disease (Blake et al 1987, Fajo et al 2009, Skirrow 1977) but does eating contaminated chicken meat cause the disease? Or can cross contamination with other food occur during preparation? Can handling live or dressed chickens increase the risk of infection? There are reports of chicken being available for sale (for example, from wet markets or supermarkets) which is contaminated with campylobacters (Abu et al 2010). This is a problem because improper cooking may allow some of the bacteria to survive (Hudson et al). Only a small number of campylobacters may be needed to infect a human host (Black et al 1988, Robinson 1981).
I am doing this report to understand what role chicken has in causing infection of humans. I am also wanting to see how chicken becomes contaminated and to see what methods have been devised that may prevent or reduce the levels of contamination. This would help to limit the risk of people becoming infected.
Campylobacteriosis (or also know as campylobacter enteritis) is a disease caused by species of bacteria in the Camplylobacter genus. They are gram negative, spiral shaped and have a flagellum at either one or both ends. Campylobacters are motile and can survive in environments with lower oxygen content than air. Most species have optimal growth at 37'C. The most common species found in humans is Campylobacter jejuni (Allos and Blaser 1995). Some species are shown in (Table 1).
Infection by campylobacters can cause inflammation of the small intestine and colon. (Allos and Blaser 1995). Fever, Diarrhoea (can be bloody), stomach pains, vomiting, nausea and headaches are all symptoms patients can exhibit (Allos and Blaser 1995, Eerola et al 2009). Some symptoms are shown in (Table 1). However, some patients may exhibit none or mild symptoms (Allos and Blaser 1995).
Contamination of chicken with Campylobacter spp
What parts of the chicken are contaminated?
It may help to prevent contamination if we know what parts of the chickens are or become contaminated. During a study, samples were taken from the muscle tissue, neck and sub-cutaneous skin, peritoneal cavity and caecal content. The study found Campylobacteria in all samples but very low levels within the muscle tissue. The study suggests that campylobacters can enter into the subcutaneous region through the feather follicles (Berndtson et al 1992).
How does contamination occur?
Contamination of chickens may occur at farms. One study looking at possible sources examined several farms. The farms had closed and open houses for the chickens. They found that chickens in open-houses had greater levels of campylobacters. They reasoned that animals, which could possibly carry campylobacters, may have access to the open-houses and thus transmit the bacteria to the chickens. Closed-house farms may prevent other animals more effectively (compared to open-houses) from entering and so would reduce the risk of the chickens becoming colonised. This would explain the lower levels of campylobacters (Abu et al 2010). C. jejuni were found in the faeces of chicken found at a farm. They found no evidence of C. jejuni in newborn chicks, but within 5 weeks all chickens were infected. It was suggested that C. jejuni was spread horizontally through the faeces. Evidence of C. jejuni was also found in the water supply, suggesting another source of the bacteria (Ono and Yamamoto 1999).
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Contamination may occur in the slaughterhouses. There may be many factors which contribute to the contamination of carcasses. A study performed looked at several areas where chicken could be infected with campylobacters. It looked at two types of slaughterhouse: conventional and automated. Samples of chicken from both types were found to have high levels of contamination by campylobacters. After slaughtering, all chicken were found to be contaminated, even though some were Campylobacter-negative before entering the slaughterhouse (Abu et al 2010). Another study seems to support that contamination occurs in slaughterhouses. The results show contamination present on chicken carcasses during the process of slaughtering (Ono and Yamamoto 1999).
There is evidence for contamination during the slaughtering process. A study (Allain et al 2010) collected a chicken carcass and the caeca from several other chickens, from many batches of chicken slaughtered at different slaughterhouses. Analysis of these found that there was a greater level of campylobacters on the carcasses than in the caeca. This suggests that the contamination is increased during slaughtering. They also found that chickens slaughtered later in the day have a higher chance of becoming contaminated. Before the slaughter, the area would have been disinfected and cleaned, so the first batch would have had a lower chance of contamination. As the day progresses and more chickens are slaughtered, the likelihood of infected chickens being slaughtered and contaminating further batches increases.
Viscera rupture is a source of contamination. This can be where the intestines are split, spilling faecal matter out. As there are campylobacters present in the gut of chickens, this means risk of contamination is possibility. Rupture of this kind occurs because slaughterhouse machinery is not designed in such a way to cope with variations in chicken size and so can become damaged Christensen et al (2006).
Results from a study by Ono and Yamamoto (1999) indicate extensive contamination of the slaughterhouse (Table 2). Many of the parts may come in contact with the chickens and transmit the campylobacters.
Defeathering has been implicated in the contamination of chicken with campylobacters. A study found more campylobacters on chicken carcasses after the defeathering process than before (Berrang et al. 2004). Another study also found evidence for an increase after defeathering (Ono and Yamamoto 1999). During defeathering, the chicken carcasses can be scalded to open the follicles, which aid the removal. The opening of the follicles would enable campylobacters to enter. This could prevent removal of all the bacteria if the skin of the carcass was disinfected. If the disinfectant does not fully penetrate the follicles, bacteria would still be present. (Berndtson et al 1992)
Chicken can become contaminated by airborne micro organisms (Ellerbroek 1997), which may include Campylobacter. In a study by Berrang et al. (2004) chilled carcasses of chicken were hung in the feather-picking room to collect any airborne campylobacters. They found that there were campylobacters present on the exposed carcasses after the defeathering process. This seems to agree with a previous study which reports the feather plucking room to be an area of risk with respect to airborne microbial contamination (Ellerbroek 1997). However, Berrang et al. (2004) compared the levels of campylobacters on the exposed and non exposed carcasses and found no significant difference. They also used Petri dishes filled with an agar to examine the level of campylobacters in the air. The results from the Petri dishes indicate that although campylobacters are present in the air, they are present in a low quantity. They concluded that they found no evidence that airborne contaminants cause a significant increase on the amount of campylobacters on the carcasses. This suggests that although there is a risk of airborne contamination during defeathering, there is a low risk of campylobacters.
Temperature seems to have an effect on Campylobacter contamination. A study found that at temperatures higher than 15'C, the level of contamination on the carcasses increased. The article mentions that because most slaughter houses do not regulate the temperature inside it should be similar to outside temperature. They suggest that the seasonal variability may affect the level of contamination (Allain et al 2010). One paper set out to find how environmental factors affect the risk of campylobacters. Temperature and humidity were found to have an effect. They concluded that their results confirm campylobacters are most prevalent in the summer (White et al 2009).
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How is it transmitted to humans?
Infection occurs after ingestion of campylobacters, as shown by some studies (Black et al 1988, Robinson 1981). This may suggest that infection can occur from chicken directly (i.e. by eating contaminated chicken). It may also occur indirectly, with the bacteria contaminating other food (e.g. salads) which is subsequently eaten.
Raw or undercooked meat could pose a risk of causing infection. Chicken bought from retail markets (both wet market and supermarket) were found to be contaminated with high levels of campylobacters (Abu et al 2010). Another study also indicated presence of campylobacters in retail chicken (Ono and Yamamoto 1999). If chicken meat isn't fully cooked, campylobacters may remain and become ingested, leading to infection. (Berndtson et al 1992, Graham et al 2006).
In one study, live chickens seem to be the source of infection for three people. The strain of CAMPY isolated from the chicken faeces seemed to be identical to that of those people. The same study found strains of CAMPY on dressed chicken which were the same as those infecting another three people (Skirrow 1977). This may indicate cross contamination with food eaten because of unsatisfactory hygiene.
Measures for control
There is a risk that Campylobacter-contaminated chicken could cause Campylobacteriosis in humans. There needs to be ways in which to limit the amount of campylobacters on the chicken, whether by preventing initial contamination, killing or deactivating campylobacters that have already contaminated the chicken or by another way.
Coriander oil has been suggested as a possible method for control. A study wanted to see the affect essential oils would have on C. jejuni. They prepared several types of oil for use on sterilized chicken and beef. After applying the oil, they inoculated the meat with C. jejuni. They found that all the oils had some inhibitory action upon C. jejuni. The bacteria were able to resume growing when removed from the oils of Basil, holy Basil and fingerroot. Bacteria in the other oils however, did not start to grow again, suggesting that they have been killed or severely damaged. Coriander oil seemed to have the greatest antimicrobial affect. Coriander oil had a similar effect on both chicken and beef. The oil was unaffected by use at different temperatures (the two used in the study were 4 and 32'C) (Phumkhachorn et al 2010). Coriander oil would be highly useful in controlling campylobacters in food. Phumkhachorn et al (2010) mentions several points about the oil, including its low cost and suggests it as an alternative to the chemical inhibitors used now.
Carlton et al (2005) performed a study to see whether the use of bacteriophages is an effective means for treating campylobacters. Phage treatment was tested to see if it has an effect before (group A) and after (group B) chickens were infected with C. jejuni. Group C were control chickens which received only phage treatment. Group D were control chickens which received only C. jejuni. The chickens were euthanised at regular intervals and the caecal contents were examined. Their results showed that the group A chickens became infected, showing that the phage did not prevent initial infection. They did however find that the colonisation of C. jejuni was delayed in group A. The levels of C. jejuni were found to be lower than that of group D. The group B chickens show sudden decline after starting phage treatment. After treatment, C. jejuni were found to rise to a similar level as that of group A. Group C showed that the phage cannot remain in the cecum without C. jejuni. Group D showed levels of C. jejuni much higher than phage treated groups. The phage seemed to have no detrimental affect on the chickens as nothing was observed to suggest this. Carlton et al (2005) indicated that more work and studies need to be done before the phage can be used commercially. They mention how it would be important for phage to be inactivated because it may form an equilibrium with the C. jejuni and may not have the desired effect.
There are procedures which the consumer can perform to help limit exposure to the campylobacters. It's fairly common knowledge that good hygiene may prevent infection. Washing hands thoroughly after handling raw chicken could prevent cross contamination. If the chicken skin was removed prior to cooking, this could help reduce the level of contamination. However, there would still be Campylobacteria present on the surface of the peritoneal cavity so there remains a risk if undercooked (Berndtson et al). Micro organisms may be able to survive on food which has been cooked at a low temperature or only heated for a short period of time. A study into chicken livers showed that it took 2 to 3 minutes, when pan frying, for the core temperature of the liver to reach 70-80'C. Campylobacters were inactivated after 5 minutes at this temperature. This indicates that undercooked or raw chicken (liver or otherwise) could still be contaminated with campylobacters and so has a risk of infecting the consumer (Graham et al 2006).
The papers read for this study seem credible with nothing obvious indicating the results are unreliable. Results from separate papers generally indicate the same conclusions. There is a slight difference in the results of Ellerbroek (1997) and Berrang et al. (2004) but that is because Ellerbroek tested for other micro organisms and not campylobacters.
Evidence from the papers suggests that chicken is a potential risk for transmitting campylobacters to humans. Entirely preventing initial colonisation may be unfeasible, but there are many parts which could be altered???
At the farm level, restricting the access wild animals have to the chicken houses could help reduce colonisation by campylobacters. Treating drinking water for the chickens could also aid reduction. Both points may merit further investigation. Results from additional studies into other sources of campylobacters could enable better control over the colonisation of chickens.
The evidence shows slaughterhouses can greatly contaminate chicken. This can be because of the presence of campylobacters on parts which touch chickens (e.g. fingers of defeathering machine). It seems unlikely that contamination of these parts can be prevented entirely, however studies into how to minimise the spread of such contamination (e.g. cleaning equipment after each batch of chicken have been slaughtered and seeing the effect what this has) may provide options for control. However, the cost needed to do this commercially would also need to be looked into ' it is unlikely that the methods would be adopted if the cost is too high.
Seasonality has been indicated to have an effect on campylobacters contamination. Further studies into why this is would be useful.
Studies into ways to administer phage to chickens effectively and the costs involved in doing so would be useful. Coriander oil could be cheaper to produce and possibly safer to use than the disinfectants and other chemicals currently in use to control campylobacters. Studies should look into this because initial results seem promising. Although it's generally common knowledge that heating food can kill bacteria and that good hygiene helps reduce risk of infection, some members of the public may not know. It may be A GOOD IDEA to educate the public about this. There are multiple species and strains of Campylobacter and the treatments suggested may not have identical effects on each species or strain. Some (e.g. thoroughly cooking food) will probably work on each but others (e.g. phage treatment) may not have the desired effect. Research into the effects of treatments on other CAMPY could inform us into how to combat a range of species/strains.