Abundance and Risk Factors for Dermatobiosis in Dairy Cattle of an Organic Farm in the Tropical Region

2.1. Dermatobia hominis: Geographical distribution and biology

According to [2], flies of the species D. hominis are diurnal and are found in tropical forests. According to [3], flies of D. hominis were never found in stables and houses, being more abundant on the edges of woods, forests, and eucalyptus plantations. As [4] says, this fly is well adapted in Brazil, mainly concentrated in regions of hot and humid climate, with abundant vegetation and in altitudes lower than 1000 meters. According to [5], the life cycle of D. hominis has two well-defined stages. The nonparasitic stage corresponds to the soil pupation and adult flies in forest, and the parasitic stage corresponds to the entire development of larvae in the subcutaneous tissue of the host. The flies copulate in the first 24 hours after their emergence. Few hours after fertilization, the females begin to frequent the vicinity of cattle corrals, meeting several species of fly vectors. The deposition of their eggs is made during the flight in the lateral–ventral region of the vector after its capture and immobilization. The incubation period of eggs in the vector is of approximately eight days, and when this vector meets the host, the larvae break the eggs and penetrate through the hair follicles into the skin causing nodular myiasis. The larval period can go from 25 to 60 days. It is at night or early in the morning that mature larvae leave the host and go to the ground to pupate, avoiding the sun.

In Colombia, [6] observed higher prevalence of D. hominis in rainy season. [7] reported the occurrence of dermatobiosis throughout the year in Argentina, with infection peaks in rainy season, with warmer temperatures and higher humidity. [8] observed a higher incidence of infestation by larvae of D. hominis in the months of November and March, in São Paulo, Brazil, with decreased incidence until June. Larger infestations by warble were verified in March and April, in the state of Paraná (Brazil), with lower incidence in August and September, according to [9]. The authors linked the higher incidence of this parasitosis with rainy season. As [10] says, the highest prevalence of D. hominis during the rainy season is due to the better development conditions for the parasite, where a greater number of larvae can reach the pupal stage.

[11] described that the warble is distributed in approximately 20 states in Brazil, with higher abundance in Rio Grande do Sul, Santa Catarina, Paraná, Rio de Janeiro, Espirito Santo, Distrito Federal, and Goiás. The author mentions that the parasite does not occur in the states of Amapá, Rondônia, Ceara, Rio Grande do Norte, and Sergipe. According to the author, the soil conditions in these places do not offer conditions for the parasite to complete its life cycle. According to [4], D. hominis life cycle is complete in 80–150 days.

Observations related to seasonal variations in D. hominis in the city of Governador Valadares, Minas Gerais, made by [12] revealed that there is a positive correlation between parasitism by larvae D. hominis, relative air humidity and rainfall. However, no relationship was observed between ambient temperature and parasitism rates. Seasonality studies of the warble in cattle from the city of Guaíba, RS, mentioned by [13] have shown that in the warmer seasons of the year, that is, during the spring and summer, infestations happen with higher intensity. [14] in surveys conducted in Campo Grande – MS observed higher rates of warble infestation in periods of higher rainfall and higher relative humidity, with no positive correlation between ambience temperature and infestations in animals and also reported the presence of larvae throughout the study period with maximum amounts in March and May.

By studying the seasonal fluctuation of D. hominis in bovine skins coming from slaughterhouses, [15] observed that the highest percentages of infestation occurred when the months before had recorded increases in average temperature and rainfall. These factors may favor the penetration of larvae in the soil decreasing the pupation time of D. homins larvae. In addition, such climatic conditions also benefit its vectors’ pupation.

In southeastern Brazil, the months of spring and summer, which correspond to the rainy season, are the most favorable period of year for the occurrence of dermatobiosis in cattle. Smaller infestations happen during the dry season in the months of autumn and winter according to [16] and [17].

According to [18], in Brazil, losses caused by of D. hominis larvae reach 250 million dollars per year.

2.2. Body distribution of Dermatobia hominis larvae

A study on variations related to infestations of cattle by D. hominis larvae was held in Viamão – RS by [19], when the author observed higher incidence of warble in the anterior left part of cattle. [13] observed that, in cattle, 73% of subcutaneous nodules caused by D. hominis larvae were distributed in the anterior parts. The most infected parts were the ribs (31.9% of the observed nodules), scapula (21.5% of the observed nodules), forelegs (17.8% of the observed nodules), and neck (8.8%).

[20] verified the parasite dynamics of warble, noting its incidence in relation to decubitus in cattle of the Canchin race, in São Carlos – SP. The incidence of parasitism was higher on the left side (14.2 nodules on average) compared to the right side (10.5 nodules). According to the author, the higher incidence of parasitism on the left side can be explained due to the fact that this region was more exposed to the vectors of D. hominis’ eggs. In his observations it was possible to say that most of the animals during their rest leaned on their right side, that is, 2.360 animals observed, 1.183 had the habit of lying on their left side, while 1.447 were lying on their right side. In another study, [21] found that the regions of the forelimbs and the left blades were more parasitized. According to the author, low parasitism in posterior regions was due to the tail, which acts as a broom protecting such areas up to approximately the seventh rib. The data showed that, although protected posterior regions are equivalent to 41.06 % of the body surface of the animal, only 16.20 % were infested by warble. In another study by [22], in the city of Seropédica in the state of Rio de Janeiro, it was observed that the body region with the highest number of nodules was the blade, followed by the ribs and the forelimbs. It was also observed that, in cattle antimeres, the left side had 50.46 % of the nodules, and the right side 49.54 %. But this difference was not statistically significant. [23] conducted a study regarding the seasonal fluctuation of larvae D. hominis on cattle skins from slaughterhouses, observed a higher incidence of nodules caused by the larvae of D. hominis in the anterior region, with a 97.8 % rate.

[24] observed a significantly higher frequency of D. hominis nodules in females (16.7%) than in males (14.7 %). The presence of larvae in adult animals (15.4 %) is also more significant than in younger animals (12.1 %) and when it comes to the coat, the highest frequency of larvae was observed in the dark ones (black). Considering the body part, the one that was the most parasitized was the left anterior quadrant.

2.3. Organic dairy production system

In conventional livestock, the larva population on the cattle is controlled with the use of chemical larvicide; on the other hand, organic rural must meet the standards contained in the 60th Article of Normative Instruction No. 46, 2011, Ministry of Agriculture and Supply, which regulates organic production in Brazil, restricting the use of allopathic medicines [1]. The term “organic” refers to animal and vegetable food that are produced without the use of fertilizers; pesticides; insecticides; antimicrobials; antiparasitic, transgenic, or any other drug that may contain harmful residues to human health, including agricultural products to conventional dairy farms [25].

Milk production in organic systems does not reach 0.1% of national production, which is about 25 million liters per year, due to several factors, such as: rural extension work enabling the process to small producers; the lack of scientific research adapting livestock production in organic system to the tropical reality; as well as food pasture fertilizers, racial patterns, and health care with the herd, such as endo- and ectoparasites control and mastitis [26].

3.1. Location

The study was conducted from September 2009 to August 2010 in an area that belongs to the Sistema Integrado de Produção Agroecológica (Integrated Agroecological Production System) – SIPA (Fazendinha Agroecológica Km 47), technical cooperation project between Embrapa Agrobiologia, Empresa de Pesquisa Agropecuária do Estado do Rio de Janeiro (Agriculture Research Corporation of Rio de Janeiro State) (PESAGRO – Rio /Seropédica), and Universidade Federal Rural do Rio de Janeiro (Rural Federal University of Rio de Janeiro) [27]. SIPA is located in the city of Seropédica, metropolitan region of Rio de Janeiro state, currently occupying 70 hectares and incorporating, in addition to vegetable production area and fruits, a fragment of forest, a forest garden, and areas of agroforestry and ornamental species. Pastures subdivided into paddocks total 30 hectares.

3.2. Weather

The meteorological data used were temperature (T) of the air, relative humidity (RH), and precipitation (PP) obtained from the Agrometeorological station situated in SIPA’s area.

The climate is hot and humid with little pronounced winter. The average temperature of the coldest month is higher than 20 ° C (68°F) and the maximum temperature in the summer can exceed 40 ° C (104° F). The rainfall is characterized by the existence of a rainy season in summer and dry in winter. The annual rainfall is around 1.300 mm, although it is mostly rainy in spring and summer, the occurrence of prolonged drought is common in the months of January and February [27].

3.3. Animals

The herd consisted of 40 crossbred dairy animals Zebu x European (Gir x Holstein), divided into lots of young and adult animals. The young ones were divided into two further lots: suckler calves (birth to 6 months) and weaned calves (from 7 months to 18 months or 330 kg), and a lot of adult animals consisting of dry cows, in lactation, and a bull. The determination of the coat of animals followed the Girolando characterization [28]. (Figures 1 A, B, C, and D).

3.4. Management of animals

The management system was semi-intensive: the animals remained in the corral during the day, where accumulation of manure could take place, and returned to the grass in the late afternoon. A physical model for organic milk production is implemented. Throughout the management, animal welfare, including avoidance of psychological stress in the herd, is prioritized. All the pickets have access to clean drinking fountains with good-quality water and shaded areas with afforestation. Containment fences are electrified and made with flat wire, in order not to represent a risk of injury to the animals.

The pastures are used in a rotation system. To supply the smaller forage production that happens in the dry period (period of lower growth of pastures), a cultivated area is managed to offer a forage supply in the trough. It is estimated that the period of lowest forage production in the region begins in mid-June and goes on until late October; that is, 135 days (or nine Fortnights) of drought and lower temperatures at night. A dairy Gir bull is used to ensure the reproduction of cows as well as the welfare of animals.

3.5. Health Management

The health management system established was developed for the SIPA project “Fazendinha Agroecológica Km 47.” It is based on the folowing: animal welfare, strategic control of parasites, and homeopathic therapy, always stressing prevention as the most important aspect with regard to treatment. The specific objective was the reestablishment and maintenance of herd health in that organic system, and the general goal was to facilitate the structuring of an experimental organic dairy cattle system.

Homeopathic medicines have been prepared by the Pharmacy School from Instituto Hahnemanniano do Brasil. Drugs are in accordance with the rules of the Brazilian Pharmacy in the form of liquid presentation, and packaged in appropriate amber glass containers. The ways of administration are oral, nasal, or vaginal.

As already mentioned, throughout the management, the priority is the animal’s welfare, including avoiding of psychological stress in the herd. “Good management practices in dairy cattle with emphasis on preventive health” established for this breeding system follow the definitions of the 60th Article of Normative Instruction No. 46, 2011, Ministry of Agriculture and Supply.

The basic requirements under Article 60 of MAPA IN No. 46 [1] are as follows: (1) follow the principles of animal welfare at all stages of the production process; (2) keep hygiene and health throughout the breeding process, consistent with current health legislation and the use of products that are authorized in organic production; (3) provide preventive health techniques; (4) offer nutritious healthy food, with quality and in correct amounts according to the nutritional requirements of each species; (5) offer good-quality water and in appropriated quantities, free of chemical and biological agents that may compromise their health and vigor, quality product and natural resources, according to the parameters specified by law; (6) the use sanitary facilities that are functional and comfortable; and (7) dispose in an environmentally appropriate way, the production wastes.

Vaccinations against FMD, brucellosis, clostridial diseases, salmonellosis, and rabies follow the current schedule in health-surveillance Ministry of Agriculture Livestock and Supply. Homeopathy is the adopted therapy for treatment and prevention of major diseases of dairy cattle, with a Homeopathic protocol developed for this creation system.

A supplement freely provided to the entire herd was formulated according to this system, composed of salt, sulfur (for animal feeding), and dicalcium phosphate.

3.6. Monitoring dermatobiosis (berne)

Inspection was performed biweekly (mapping the presence of larvae), totaling 915 inspections. The animals were inspected by anatomical demarcation, and their body divided into antimeres: anterior upper right (RADS), anterior lower right (RADI), posterior upper right region (RPDS), lower right posterior region (RPDI), anterior upper left (RAES), left anterior inferior (RAEI), posterior upper left region (RPES), and posterior lower left region (RPEI). The presence of the larvae (Figure 2) was observed in the different regions, and the data recorded in documents, according to the methodology of [29], with modifications (Figure 3).

3.7. Statistical Analysis

The berne description of the amounts into categories of each attribute were studied, and performed some exploratory data analysis through bar charts, box plots and calculating the average number of warble per studied animal. To compare the berne counts among the quadrants defined by anatomical demarcation, we used nonparametric Wilcoxon and Kruskal-Wallis test [30], due to the presence of nonnormal data [31]. To verify the association between the inherent variables to the animals and climate we used the generalized linear bivariate model of Poisson [32]. The dependent variable was the larva counted in each animal, the independent variables or explanatory variables were related to the animal profile (gender, age, and coat) and climatic factors (average temperature, rainfall, and relative humidity). As the dates of collection were different between adults and young animals (suckling calves and weaned calves), a stratified analysis was made taking into consideration the age of the animals involved in the study. The relative risk indicator is a measure of association, where two or more variables are correlated, being one of the ways used to the assessment in epidemiological statistics to answer the correlations between two outcome and exposure variables, where RR = 1 lack of association occurred; 0 <RR <1 protection factor, and RR> 1 risk factor.

In the period of study, 915 berne counts in cattle were made (inspections), in which 391 were in adult cattle, 356 in weaned calves, and 168 in suckling calves. Of the total, 784 females and 131 males were counted. Of the 915 counts, 354 were made ​​in cattle coat with red color in typical shades, 180 in fur animals with white on black, 87 in cattle with black color coat, 198 counts in animal with light brown and dark coat, and 96 counts in animal with black on white coat.

To adjust the climate data to the study database, the average was calculated for each of them (Average temperature, rainfall, and relative humidity) taking into consideration a fifteen-day delay period preceding the collecting day.

All statistical analyses were performed using statistical package R [33].