Campylobacteriosis was the most frequently reported zoonosis throughout the European Union in 2017, and salmonellosis was the second-most common zoonosis to be reported in the European Union . In addition to Europe, the number of cases of campylobacteriosis has also increased in North America and Australia . The significant increase in the number of cases from below 55,000 in 2001 to more than 70,000 in 2016 in Germany highlights the importance of raising consumer awareness of Campylobacter. One reason for the increased case numbers could be that human consumption of poultry meat in Germany increased from 10.92 kg/head in 2001 to 13.19 kg/head in 2018 , and consumers therefore come into contact with Campylobacter more frequently. Another reason for the increasing case numbers, especially in the summer months from June to September, could be the increased ambient temperature. Yun and colleagues  showed that the increase in ambient temperature is positively associated with the occurrence of Campylobacter. Although the incidences of salmonellosis decreased from 2001 to 2016 in Germany, in 2018, the number of infections was higher than in 2016 . This shows that the success of activities to reduce the incidence cannot be taken for granted. The incidence of clinical toxoplasmosis ranged from 6 to 23 cases in the years 2002–2018  and thus remains well below the incidence of Salmonella and Campylobacter.
Since this survey was conducted by a commercial online survey company and included target panels with a stratified sample, the survey could be conducted with little effort in a short amount of time. The number of necessary participants was quickly reached, and time-consuming recruitment was not necessary. In addition, the acceptance among the participants was high, as they consciously decided to be participants in a panel, and the questionnaire could be answered online at any time of day and at any place. Data input and transmission were performed automatically so that transmission errors could be minimized. However, this did not insulate the study from forms of bias that are characteristic of online surveys. First, not all participant groups may be available online. In the event of queries, assistance may not be possible. In addition, the environment cannot be controlled during the survey. The presence of third parties cannot be ruled out, nor can the presence of other media, e.g., to provide assistance, be excluded . Answering individual questionnaires by using automated answer scripts is theoretically possible but rather unlikely. The survey is not open to the public, and each person receives an individual e-mail link that can only be used once. Although there is no 100% guarantee, the panel provider takes as much care as possible to prevent automated answers.
Our results showed that the proportion of participants who did not know about Campylobacter at all was 68.3%. This corresponds with the results of another study among consumers from Germany, in which 75% of the respondents did not know that Campylobacter occurs in food . Publications from other European and non-European countries also show that consumers’ knowledge of Campylobacter is predominantly poor. A total of 83.3% of Slovenian consumers did not know about Campylobacter . In an Australian study, only 8% of respondents knew about Campylobacter . A total of 22% of respondents in an Austrian study  and 16% of respondents in a U.S. study  had already heard of Campylobacter. In the U.S., consumer knowledge seems to have increased in recent years, since in an earlier study, only 7% of the participants had heard of Campylobacter .
Our results also showed that most consumers in Germany (> 97%) have heard of Salmonella at least once before. This corresponds with the results of another study among consumers from Germany, in which 96% of consumers had already heard of Salmonella in food . In another study with an open question about pathogenic germs in food, only slightly more than half (58.3%; n = 420) of the respondents mentioned Salmonella . Publications from other European and non-European countries also showed that consumer knowledge of Salmonella is generally good. In Austria, 98% of consumers knew about Salmonella . In Ireland, 92.9% of respondents have already heard of Salmonella . In the Netherlands, a study found that 97.4% of respondents said they knew that they could be infected with Salmonella from contaminated foods . In two U.S. studies, more than 90% of consumers had already heard of Salmonella [13, 15]. In comparison to Salmonella and Campylobacter, our results showed that the general knowledge about Toxoplasma was almost equally divided among consumers. Forty-eight percent had never heard of the pathogen, and 51.7% had at least heard of Toxoplasma. In a study from Poland in which 565 pregnant women participated, 439 (94.4%) of the respondents were aware of toxoplasmosis. A total of 77.4% knew it was a zoonosis . A U.S. study showed that 48% of pregnant women had heard or seen information about toxoplasmosis . A survey of pregnant and postpartum women in Brazil showed that only 27.8% knew that the disease existed. Most of them (72.2%) had never heard of toxoplasmosis . In a study from Zimbabwe, only 4% of 49 respondents knew that toxoplasmosis was a zoonosis that could be transmitted via cats . Overall, there appear to be fewer consumer surveys than on Campylobacter and Salmonella. This may be because clinical symptoms usually do not occur except in pregnant women. In addition, the overall case numbers are significantly lower than those for Campylobacter and Salmonella in Germany as well as throughout the EU .
Our study showed that meat was not sufficiently known as the main vector of Campylobacter. Only half (52.2%) of those who knew about Campylobacter (n = 320) knew that it could be transmitted to humans via meat. Although 116 consumers indicated that they knew how they could protect themselves, 36.2% (42/116) did not know that transmission occurs via meat. In general, consumers are aware that food-borne infections are often associated with chicken meat [34, 35], but an international comparison also shows that consumers do not know that meat is a vector of Campylobacter. An Australian study showed that only 9% of consumers associate Campylobacter with chicken and poultry . In a U.S. study, only 0.4% of respondents could name a Campylobacter vector . In Slovenia, only 18% of respondents knew how often Campylobacter was present on poultry meat in retail outlets . A study from Switzerland showed a high level of general knowledge about pathogenic bacteria in poultry meat, but pathogenic bacteria are perceived as the least threatening in comparison to other potential food risks, such as the intake of too many calories, an unbalanced diet, hormone residues in meat or allergies . In New Zealand, only 15% of respondents knew that a very high proportion of fresh chicken is contaminated with Campylobacter . In a UK study, 24% of respondents had heard that Campylobacter can cause foodborne infection .
Our study also showed that meat was predominantly known as a vector of Salmonella. Only 13.4% of all respondents (131/980) who knew about Salmonella said they did not know that these pathogens could be transmitted to humans via meat. Nevertheless, it was found that some consumers misjudged their knowledge. Of those who said they knew how to protect themselves, 11.3% (88/779) did not know that Salmonella was transmissible via meat. An international comparison shows that many consumers are aware that meat can be a source of Salmonella transmission. A survey of students at the University of Maine showed that slightly more than half of those surveyed (57.3%) were aware of an association between Salmonella and raw chicken . Murray and Glass-Kaastra  showed that the majority of respondents are aware of the risks of foodborne illness associated with chickens, and the majority are aware that chickens that are not fully cooked can be a cause of foodborne illness. A study in Mexico showed that fresh meat is the most commonly considered sources of salmonellosis compared to other food categories, such as “fruits and vegetables” or “dairy products” . In an Italian study, on the other hand, the awareness of Salmonella transmission was not particularly high. Only approximately ¼ of the respondents were aware of food vehicles for the transmission of Salmonella . In Ireland, a study showed that of those who knew about Salmonella, only 23.1% knew that Salmonella can be transmitted via poultry. Only 4.7% knew that Salmonella could be transmitted via pork. The most frequently mentioned possible vectors that were correct were eggs (44%) .
In our study, 50.7% knew that Toxoplasma could be transmitted via meat. Thus, we can conclude that consumers know more about the transmissibility of Toxoplasma via meat than about the transmissibility of Campylobacter via meat. A U.S. study showed that only 30% of pregnant women were aware that Toxoplasma may be found in raw or undercooked meat . Another U.S. showed that only 24% of the respondents knew that Toxoplasma can be transmitted via food . In a study from Poland that included only pregnant women, 46.7% knew that raw or uncooked meat was a route of transmission . Nevertheless, it is also evident that significantly fewer consumers (16%) know that Campylobacter can be transmitted via food. Again, most consumers (93%) know that Salmonella can be transmitted via food .
Since the consumption of meat is known to be the main cause of Campylobacter infection, a reduction in meat consumption could lead to a reduced incidence of Campylobacter food-borne infections. A general reduction in meat consumption would also have the advantage of a lower number of Salmonella and Toxoplasma infections, although consumer knowledge of these pathogens is higher. Clinically manifest diseases or even deaths associated with the consumption of meat, and therefore secondary health care costs, may be reduced if knowledge about foodborne diseases were more widespread. Switching to a vegetarian diet would also reduce infection with these pathogens, as meat is the most common source of foodborne infections. A complete reduction in incidence is not possible because Campylobacter is also transmissible through raw milk  and Salmonella through eggs .
In addition, only 11.5% of the participants in our study who had heard of at least Campylobacter (n = 320) knew how to protect themselves from Campylobacter infection. Thus, it is not sufficient only to increase the level of knowledge about Campylobacter. In Germany, there are still too many consumers who do not wash their hands or the cutting board after preparing raw meat . This result seems contradictory at first, since a survey of the German Federal Institute for Risk Assessment shows that 90% of the respondents indicated that they know how to protect themselves against pathogenic bacteria in their own household. At the same time, this survey also shows that only a minority of 9% of German consumers believe that compliance with kitchen hygiene serves as a protective measure against bacteria . International comparative studies show that consumers are well aware of good hygiene practices and that many consumers are familiar with hygiene measures, such as washing their hands after handling raw meat [43, 44]. One reason for the nevertheless increasing incidence of foodborne infections in general could be that consumers do not wash their hands properly, and cross-contamination still occurs . Health policy has long recognized that insufficient consumer awareness of Campylobacter is a problem, and scientific institutions have already compiled comprehensive information for consumers. However, although much information about Campylobacter and protection against infection is available at the national and international levels [46,47,48,49], our results suggest that the available information does not reach consumers. Consumers must actively search for available information material. Increased media attention could increase consumer awareness and vigilance in food handling . The general lack of dramatic outbreak situations for Campylobacter explains why media attention is rather weak. The total number of Campylobacter outbreaks is much lower than that of Salmonella infections. The number of people who need hospital treatment due to clinical symptoms is much lower for Campylobacter than for Salmonella . Regarding Campylobacter, 3% of the patients need to be hospitalized, whereas this is necessary for 19.5% of Salmonella patients. In addition, low mortality has occurred in those with Campylobacter infections than in those with Salmonella infections .
Providing a label with appropriate handling instructions or warning signs indicating the Campylobacter risk could increase consumer awareness. This is confirmed, for example, by the results of other consumer surveys [11, 50]. Approximately 80% of consumers in Germany have the opinion that it is not easy to discern whether a foodstuff can cause health problems if handled incorrectly . According to the results of the Deutsche Landwirtschafts-Gesellschaft e.V ., which informs consumers about the quality of food (among other things) and conducts studies on the food industry, consumers in Germany think that such information on the packaging would be very useful. It is therefore necessary to identify methods to ensure that the available information materials reach consumers.
According to the Robert Koch Institute case numbers of Campylobacter, men are generally more exposed to infections than women . However, in our study, we could not show that men were significantly less informed about Campylobacter than women. Therefore, we could not confirm any association between the level of knowledge of men and women and the incidence of the disease. This is also coincident with results from Lin et al. . Women are significantly more interested in food safety issues than men, although there is no statistically significant relationship between gender and food safety knowledge . This is confirmed in other studies [54, 55]. Rossvoll et al.  came to a different conclusion: according to their results, men seem to know less about food safety than women and have more knowledge deficits in hygiene practices. It has also been shown that there are knowledge differences between men and women regarding the fact that microorganisms are the cause of food-borne infections . Tomaszewska et al.  found different results in two different countries in their study: while in Poland, women showed a slightly higher level of knowledge about food hygiene than men, this significant gender difference in knowledge could not be established in Thailand.
Younger consumers are less interested in food safety issues than older consumers are . This could explain why the knowledge about Campylobacter in our study differed statistically significant by age group, and young adults < 20 years were the least informed. A possible explanation would be that approximately 80% of the female and over 80% of the male 19-year-olds still live in their parents’ households . In addition, 30% of individuals under 19 years old in Germany generally do not prepare their meals themselves, whereas those over 60 years old cook more often than the average person . Children may not be as concerned about food safety and the transmission of pathogens through food because the parents often prepare the food for the children even if they are already grown up. In comparison to our study, Lin et al.  found that the age groups investigated in their study did not differ significantly with regard to Campylobacter knowledge. Similarly, Stratev et al.  could not establish a significant relationship between age and knowledge of food safety.
We found that consumers with a higher education level were significantly more informed about Campylobacter than those with lower education. Similar results were also shown in a U.S. study. Consumers with at least some college education are more likely to have heard of Campylobacter than those with less education were . Further study results also suggest that the more educated consumers are, the better their knowledge of food safety [55, 61]. However, Zorba and Kaptan  found no significant correlation between educational level and food safety issues.
Comparable to our study, other studies have not found that consumers with higher household incomes after taxes are significantly better informed about Campylobacter than are consumers with lower incomes . However, there are also studies showing that safe food handling is more prevalent among consumers with higher incomes .
We could confirm that actors in the food chain, and veterinarians in particular, are better informed about Campylobacter than are those who are not or have not been active in this sector. We have assumed that there is a certain level of knowledge about pathogens that occur in the immediate occupational sector. A study from Ontario that surveyed actors and veterinarians involved in pig production showed corresponding results. More veterinarians were familiar with Campylobacter and other microbial hazards than were individuals in other occupational groups. One explanation seems to be that veterinarians are informed about pathogens through their education and that knowledge about zoonosis is an important component . However, our finding that more than half of the actors in the food chain (54.7%) did not know about Campylobacter at all was very interesting. One survey showed significant gaps in the knowledge of Campylobacter among broiler chicken producers. While 82.4% of those surveyed know that Salmonella could be transmitted to humans via contaminated chicken meat, only 21% of chicken meat producers knew that the same applies to Campylobacter . A survey of pork producers showed that knowledge of Campylobacter is also low among this group. Only 12.8% of respondents knew that Campylobacter could infect humans . There also seem to be gaps in the knowledge of food workers in meat processing plants. While there is a high level of knowledge of general protective measures, most workers are not well aware of specific diseases or pathogens that could be transmitted through food . A U.S. study from Pennsylvania also showed gaps in the knowledge of poultry product vendors about pathogens and cross-contamination during poultry processing .
Although there are statistically significant differences in the level of knowledge by age group, educational level, occupational group and status as a veterinarian, there must be other factors that significantly influence the level of knowledge.