By way of introduction, it can be mentioned that urban and peri-urban animal production exists in different countries of the world^1,2, it is a source of occupation in which interrelations between social, cultural, economic, religious and health factors are established³, within it swine farming is a strategy to mitigate poverty⁴, since the swine is an ideal animal for urban environments with minimum space requirements, versatility in food consumption and easy commercialization.

Many of the swine producers located in urban environments are considered small-scale swine producers, that is, those who own up to 575 animals or up to 50 sows⁴. These small-scale farms (SSF) in urban conditions are associated with disease transmission, environmental pollution, lack of animal welfare and causing negative effects on public health⁵. Although there are several factors that may predispose these types of farms to the occurrence of diseases⁶, little is known regarding the biosafety factors to prevent them from the presence of diseases⁷. This determines the importance of having a correct diagnosis of the situation in these farms, especially in health and environmental impact aspects, since, to guarantee the production of these farms, it is necessary to know the potential impact on animal health.

In the northwest area of Mexico City, there are SSFs that have been immersed in urbanization, a specific example are 14 swine producers located in the borough of Azcapotzalco, who years ago began raising their animals in a rural environment but are currently in a critical situation regarding the impact of their activity on neighbors and the authorities, who assume negative aspects in health, animal welfare and environmental impact. As an objective of this work, it is considered basic to establish a guide to carry out the process of quantitative evaluation of zootechnical, biosafety and preventive medicine practices that may be a health risk for this type of farms, in order to subsequently establish palliative measures or administrative decision-making². The instrument has been modified for use on small-scale urban farms and is the first exercise of its kind.

The work was carried out in 12 small-scale swine farms (SSF) located in the borough Azcapotzalco of Mexico City, which represent 85 % of the total number of farms registered with the local association of swine producers. The farms selected were those where producers assumed the status of cooperators, upon request and interview, and which are registered in the International Livestock Individual Identification System (SINIIGA, for its acronym in Spanish). The units evaluated had a minimum of 10 animals and a maximum of 299 and represent a percentage of the swine population consistent with what was indicated by other authors^1,8.

Initially, the information obtained was that regarding the time of operation of the farm, the space of the farm, if it adjoins houses, who cares for the farm and if it has veterinary advisory. Subsequently, one or more visits were made to each farm accompanied by the application of an in situ evaluation instrument, carried out by a single evaluator according to the methodology used in similar studies^9,10. The farms were classified into fattening (T1) or full cycle (Type 2). In addition, they were classified into three groups based on the number of animals: A those with 1 to 40 animals, B from 41 to 100 and C from 101 to 300 animals¹⁰.

The instrument was applied on a farm as a test to determine its operability but was not previously validated. This was designed with seven sections with a total of 55 questions; each item was confirmed by the evaluator in the physical inspection he made on the farm; each item had a value of 0 when the response indicated a high health risk, 1 when it was intermediate and 2 low; some items, due to their characteristics, only had the options of 0 and 2. The maximum value of points obtained for each section was: biosafety (B) 12 points, preventive medicine (PM) 20, facilities (F) 12, feeding (Fe) 14, management (M) 12, health state of swine (H) 16 and environment (E) 14 points, giving a total of 100 points for T1 and 92 for T2. During the visit, the inventory of animals was checked and the population density in each farm was calculated.

Because farms could obtain a different number of points depending on their type (T1 or T2), the percentage of points obtained in general and by section was calculated for each farm. To establish the difference between the percentage of points of T1 and T2 in general and for each section, the transformation of the percentages was made obtaining the square root of the arcsine; the data thus obtained were analyzed by means of a Wilcoxon test. Similarly, the differences in percentage of points for the three population levels (A, B, C) were analyzed using the Kruskall-Wallis test, and in case of finding statistical differences, a mean difference test was performed using the honest Tukey test¹¹. Correlations between the percentage and total points obtained with the number for each farm, as well as between the population density with the percentage of points and the total points obtained, were made by means of the Spearman correlation coefficient¹⁰. Data were analyzed using the JMP.8 statistical package¹².

As results, the general conditions of the farms are initially presented, which are detailed in Table 1, where it is summarized that the farms have been operating for a minimum of 18 yr, with a variable space below 600 m², only one has workers hired, 90 % are surrounded by houses and 40 % of them do not receive any type of technical advisory.

Data from five farms T1 and seven farms T2 were obtained. Table 2 presents the total points and the percentage of points obtained in general in each farm, as well as the type of farm according to its production, where it is observed that the lowest percentage of points obtained occurred in farm 6 with 31.52 and the highest in farm 12 with 66.00. By type of farm, the highest percentage of points for T1 was 50 % and for T2 66.0 %. The percentage of points obtained by each farm is shown in Table 3.

No differences were found between farms T1 and T2 in terms of B, PM, F, Fe, M and E; however, a difference (P= 0.002) was found between farms T1 and T2 in the section focused on health state (H) (Table 4).

The relationship between the population density per m² with respect to the total maximum points reached by the 12 farms was analyzed, without finding an effect (R ² , 0.03; P=0.854). In the correlation between the percentage of points obtained and the number of animals existing on the farm, no effect was found both generally and by sections (R ² , 0.13; P=0.722). In relation to the average percentage per section for each classification of population size, only a difference in section A was detected (Table 5).

The items that obtained a score of 0 and 1 were considered as deficiencies in the production process of the farm, they may indicate a risk for the occurrence of diseases and are areas of opportunity for work on the farm. Table 6 shows the number of producers who have weaknesses based on each of the questions of the instrument.

When analyzing the items that obtained a score of 0 or 1 in B, no farm has quarantine and half of the producers do not have a bathroom or dressing room. In PM, the fact that in all farms there is the presence of other domestic species stands out. In Fe, the design, installation, quality of feeders and drinkers was considered as a planning deficiency, since only one producer has suitable feeders, and none of the farms had suitable drinkers. On no farm were the floors dry and with a finish suitable for the comfort of the animals found.

In Fe, only two farms use a combination of alternative and balanced feed for the breeders, while the rest only supply alternative feed and no producer performs a treatment of this type of feed. In M, only in a farm there is an "all-in all-out system" and an infirmary area. In H, it is a risk factor that 83 % of the farms presented respiratory signs in various areas of production and in 50 % diarrhea was observed. Finally, in E, it was observed as the main deficiency that none of the producers treats excreta and does not have an adequate disposal of biological and chemical waste. As for inorganic waste, only a quarter gives treatment, the rest is disposed of as urban garbage.

By way of discussion and based on the results presented, it is suggested that the information obtained from the application of the evaluation instrument may present biases as it happens with this type of works and as reported by other authors^1,6,10. Similarly, the lack of validation of the instrument in urban and small-scale farms establishes limitations in the interpretation of the results.

Most of these farms are dedicated to the full cycle, contrary to expectations, since it is pointed out that the breeding of fattening swine requires a minimum of facilities and the cost of accommodation for the full cycle is the most expensive part of the system, since specific constructions are needed for all the biological stages of the swine¹³. On the other hand, these results correspond to what was presented by authors who reported that full-cycle farms have better economic returns than piglet-producing and fattening farms¹⁴.

The tasks of the farms evaluated coincide with other authors who point out that the work is carried out by family members and in most cases the breeding of animals is not the only economic activity^14,15, but it was found that they were elderly people, which contrasts with what was mentioned by the same authors in other non-urban farms in central Mexico, whose owners are of economically active age and have higher schooling¹⁴.

Deficiencies in biosafety, facilities, vaccination and transport, among others, increase the risk of introduction of pathogens to the farm¹⁰, so it is necessary to detect critical points on each farm to increase biosafety and reduce disease transmission¹⁶.

The fact that no farm has quarantine increases the risk of disease transmission to the population and represents a fundamental failure in biosafety¹⁷ and is the greatest risk for the introduction of pathogens to the farm. Similarly, the absence of dressing rooms represents a break in biosafety protocols¹⁸. Although it is understood that the income of this type of farm limits investment in biosafety measures, it is important that each of them establishes practices that mitigate the risk of disease transmission; perhaps the most important thing is to raise awareness among producers to buy animals of the same origin and prevent the entry and exit of people to the farm without basic hygienic measures.

Deficiencies in the quantity and design of drinkers and feeders affect water consumption and the obtaining of nutrients, which can affect the health of animals¹⁹. The conditions of high humidity and low temperature found in 50 % of farms predispose to pneumonia, skin diseases, presence of parasites, feed consumption and hoof injuries²⁰. Another condition that predisposes to the existence of diseases is the state of the floor, which can be a factor in the occurrence of diseases because a floor with cracks makes it difficult to wash and disinfect it²¹.

Another aspect that can be associated with the existence and transmission of diseases is the almost widespread use of kitchen waste in swine feeding; this type of practice increases the appearance of zoonotic diseases, a risk that is run when animals are raised near houses, especially when used without treatment²².

The low score in management aspects indicates that modern practices based on the physiology of the animals are not used in the SSFs in swine care, which is in agreement with various authors^6,23; this idea is reinforced in this study, since most of the producers do not have an infirmary and the sick swine are distributed among the population.

A point in favor of the farms evaluated is that not regrouping reduces the stress that this represents and therefore the immune status of the swine could be better, which reduces the possibility that they get sick and can transmit pathogens to other populations^24,25. The space required per animal in the farms evaluated was correct and does not represent a situation that predisposes to the occurrence of diseases²⁶.

The difference in the percentage of points obtained between fattening and full-cycle farms in the section “Health state" indicates that the purpose of the farm influences the occurrence of diseases, the main disadvantage of the fattening system lies in having animals of different age and origin²⁴, since the risks of buying from several suppliers of piglets¹⁷ are known.

Based on the results of the study, it can be thought that SSFs are a risk for disease transmission, since the absence of protocols for biological, inorganic and chemical wastes and the lack of treatment of solid or liquid excreta represents a risk to public health and other swine populations^27,28. In addition, the management of waste in a small space and close to houses impacts the environment by dispersing or pouring uncontrollably²².

Although the size of the farms did not influence the score obtained in Fe, a negative difference was found in farms with less than 40 animals; this is explained by the fact that producers with few animals use alternative feed without treatment, do not invest in feeders and feed in a rationed form, which decreases the health state²⁹.

It is concluded that the methodology for the evaluation of the conditions predisposing to diseases in SSF in an urban environment by means of a numerical score proved to be applicable to the farms. As advantages of the application of the instrument, the following can be cited: establishing an orderly structure to carry out the inspection of the farm and having basic information for the detection of areas of opportunity to mitigate these risks and implement more accurate diagnostic methods. The disadvantages of the instrument are that it can offer varying results from one farm to another and that the evaluation of the farms would have to be carried out in a higher number of farms and validate the information of the instrument. Preliminarily, it was observed that the type of production, the size of the farms and the population density are not a factor in terms of the numerical score that was obtained, but the health state differs if the farm is full cycle or fattening; it was identified that in farms with a smaller population, feeding aspects are a risk factor for the occurrence of diseases.

The authors declare that they have no conflict of interest.