The proximity of such animals to humans has become a public health issue, since they are carriers of several infectious and parasitory diseases (BRASIL, 2006). Research made in different states of Brazil, including Paraná (PR), Sergipe (SE) and Minas Gerais (MG) has observed prevalence of intestinal parasites in synanthropic rodents (Porta et al., 2014; Guimarães et al., 2014; Mati et al., 2014). This study surfaces the importance of synanthropic rodents in the transmission chain of different parasite related illnesses to humans and other animal species.

The Strogyloide nematode belongs to the Strongyloidae family (Rey, 2001) and comprises more than 52 nematodes that parasite vertebrates (Costa et al., 1997). The disease known as strongyloidiasis is a parasitosis. It is estimated that 370 million people throughout the world are infected with it (Buonfrate et al., 2014). In Brazil, it is one of the most prevalent parasitic diseases (Sudré et al., 2006). It infects farmers and farm workers, immigrants and travelers who visit endemic areas, and also children exposed to contaminated soil (Costa et al., 1997).

This parasite infects humans through skin penetration, and has a complex life cycle involving 2 stages of development: a phase of free-living that occurs in the environment, good conditions of temperature and humidity, and the other stage as a parasite, which occurs within the host (Paula and Costa-cruz, 2011).

Infection rate varies according to the studied region and method chosen for the diagnosis (Costa et al., 1997). The clinical characteristics of strongyloidiasis are connected to the degree of parasite infection, nutritional status of the host and absence of other gastrointestinal parasitosis (Machado, 2003).

The presence of parasites inside the gastrointestinal tract may cause reduction of villi and microvilli. This reduction can cause decreased absorption and malnutrition. The jejunum is a portion of the small intestine whose function is to regulate motility and absorption of nutrients. Another factor responsible for the adequate growth of the animal is the quality of food provided, as well as the capacity to use these nutrients. It is well known that malnutrition affects several organs and is correlated to low body weight (Torrejais et al., 1995; Natali et al., 2000; Zanim et al., 2003).

Morphological alterations caused by malnutrition have been extensively assessed, demonstrating a reduction of thickness of the intestinal wall layers, reduction of the tunica mucosa (Rodrigues et al., 1985; Brandão et al., 2003; Hermes et al., 2008), villi length (Firmansyah et al., 1989; Gurmini et al., 2005), crypt depth (Firmansyah et al., 1989;  Hermes et  al.,  2008),  and  tunica  muscularis (Torrejais et al., 1995; Brandão et al., 2003; Azevedo et al., 2007).

Within this context, the present study aimed to assess the morphometric alterations and variation in goblet cells of the jejunum of synanthropic rodents infected with Strongyloides spp. compared to non-parasite infected rodents.The order Rodentia is the largest mammal group alive, with 2,277 known species, comprising 42% of the mammal  biodiversity   in   the   world  (Don  and  Reeder, 2005). Rodents are divided into 34 families (Musser and Carleton, 2005); in Brazil there are three species of the rodent family Muridae:  Rattus rattus, Rattus  norvegicus and Mus musculus. Most rodent species live in wild environments, in nature, being part of the food chain of predators such as prey birds, snakes, and lizards. However, some species adapt better to manmade environmental conditions. These are the species considered as synanthropic (BRAZIL, 2006).

The proximity of such animals to humans has become a public health issue, since they are carriers of several infectious and parasitory diseases (BRASIL, 2006). Research made in different states of Brazil, including Paraná (PR), Sergipe (SE) and Minas Gerais (MG) has observed prevalence of intestinal parasites in synanthropic rodents (Porta et al., 2014; Guimarães et al., 2014; Mati et al., 2014). This study surfaces the importance of synanthropic rodents in the transmission chain of different parasite related illnesses to humans and other animal species.

The Strogyloide nematode belongs to the Strongyloidae family (Rey, 2001) and comprises more than 52 nematodes that parasite vertebrates (Costa et al., 1997). The disease known as strongyloidiasis is a parasitosis. It is estimated that 370 million people throughout the world are infected with it (Buonfrate et al., 2014). In Brazil, it is one of the most prevalent parasitic diseases (Sudré et al., 2006). It infects farmers and farm workers, immigrants and travelers who visit endemic areas, and also children exposed to contaminated soil (Costa et al., 1997).

This parasite infects humans through skin penetration, and has a complex life cycle involving 2 stages of development: a phase of free-living that occurs in the environment, good conditions of temperature and humidity, and the other stage as a parasite, which occurs within the host (Paula and Costa-cruz, 2011).

Infection rate varies according to the studied region and method chosen for the diagnosis (Costa et al., 1997). The clinical characteristics of strongyloidiasis are connected to the degree of parasite infection, nutritional status of the host and absence of other gastrointestinal parasitosis (Machado, 2003).

The presence of parasites inside the gastrointestinal tract may cause reduction of villi and microvilli. This reduction can cause decreased absorption and malnutrition. The jejunum is a portion of the small intestine whose function is to regulate motility and absorption of nutrients. Another factor responsible for the adequate growth of the animal is the quality of food provided, as well as the capacity to use these nutrients. It is well known that malnutrition affects several organs and is correlated to low body weight (Torrejais et al., 1995; Natali et al., 2000; Zanim et al., 2003).

Morphological alterations caused by malnutrition have been extensively assessed, demonstrating a reduction of thickness of the intestinal wall layers, reduction of the tunica mucosa (Rodrigues et al., 1985; Brandão et al., 2003; Hermes et al., 2008), villi length (Firmansyah et al., 1989; Gurmini et al., 2005), crypt depth (Firmansyah et al., 1989;  Hermes et  al.,  2008),  and  tunica  muscularis (Torrejais et al., 1995; Brandão et al., 2003; Azevedo et al., 2007).

Within this context, the present study aimed to assess the morphometric alterations and variation in goblet cells of the jejunum of synanthropic rodents infected with Strongyloides spp. compared to non-parasite infected rodents.

The animals were divided into two groups: positive group PG (n=10), with five males and five females infected by Strongyloides spp., and a negative control group NCG (n=10), with five males and five females without the presence of intestinal parasites.

Histological processing

A ring of two centimeters of each jejunum collected was fixated in Bouin solution, dehydrated in ascending series of ethanol, diaphanized in xylol and included in paraffin to obtain posterior transversal semi-sequential slices, of 4 µm thickness (Junqueira and Junqueira, 1983).

The morphometric analysis of the intestinal wall was done from images of transversal cuts dyed in Hematoxilin-Eosin (HE) and observed in optical microscope with 20x objective, used to measure villi length (base to apex), crypt depth, villi area and crypt area from the jejunum of infected and non-infected rodents (Gumini et al., 2005). Histological sections of jejunum of Rattusrattus without endoparasites (Figure 1) and those infected by Strongyloides spp. are analyzed (Figure 2). 50 measures for each parameter were done and distributed through the whole intestinal circumference, in 250 intestinal segments per experimental group.

To quantify the goblet cells, images captured from slides treated by the method of Alcian Blue pH 2.5 (Junqueira and Junqueira, 1983) were used, under 20x objective. 10 crypts of each infected and non-infected animals were analyzed, for each jejunum segment, in a total of 100 crypts per group. All the images of the transversal cuts were captured through a digital camera (Moticam 2000, 2.0 megapixel) coupled to a microscope with trinocular light (MOTIC B5). All the measurements were done using the software MoticImagens Pro-Plus, version 2.0.

Statistical analysis

The data were analyzed using the statistics software Bioestat 5.3 (Ayres et al., 2007). The parameters (animal length, intestine total length, villi length, crypt depth, villi area, crypt area, and goblet cell count) studied underwent variance analysis, analyzing between groups of rodents of the same sex. T test was used to make comparison between the averages. There was a level of significance of 5% (p<0.05).

The absorption processes are completely dependent on the mechanisms occurring in the intestinal mucosa, being the small bowel (duodenum, jejunum, and ileus) function essential to the digestive process, particularly to the absorption of nutrients. According to Reimer et al. (2010), the diet restriction may induce an increase in intestine length on the long term.

In young rodents with high parasite load, there is a delay on growth, weight loss, and intestinal occlusion, possibly inducing death. Moderate infections provoke a small inflammation of the intestinal mucosa (Negrão, 2001; Silveira et al., 2002).

Considering the averages obtained at the morphometric analysis of the villi and crypts in the jejunum (villi length / crypt depth), it was observed smaller villi and deeper crypts in the male and female rodents infected by Strongyloides spp. The size of the villus depends on the number of cells it comprises, thus, the higher the number of cells, the bigger the villus, and consequentially, the larger the area for nutrient absorption (Furlan et al., 2004).

The results obtained in this study are in accordance with thatv of Blankenhaus et al. (2011), that induced the infection of mice by Strongyloides ratti, observing moderate alterations in the small intestine, such as: slight reduction of villi and hyperplasia of crypts. In research performed by Mati et al. (2014) on small bowel of the Callithrix    penicillata     experimentally      infected    with Strongyloides stercolaris, were observed in histological analysis, alterations characterized for atrophy of the intestinal villi.

However, Zaman et al. (1980) did not observe alterations in intestinal villi of Rattus novergicus infected by S. ratti, the same was observed by Dawkins et al. (1981), who analyzed the small intestine of mice infected by S. ratti. Comparing the villus and crypt areas, it was observed a statistically smaller villi area in male and female rodents infected by Strongyloides spp. Concerning only crypt area, the difference was only significant for females. The desirable relation between intestinal villus and crypts occurs when the villi are long and the crypts are shallow, because the higher the relation between villus length / crypt depth, the better will be the nutrient absorption and smaller will be the energy losses by cellular renewal (Li, 1991; Nabuurus, 1995).

In the quantitative analysis it was observed a statistically higher amount of goblet cells in the crypts of the jejunum of male and female rodents infected by Strongyloides spp., this higher number of mucous cells may be related to the protection of the intestinal mucosa facing pathogens such as Strongyloides spp. These results are in accordance to Shi et al. (1995) that observed hyperplasia of goblet cells in hamsters (Mesocricetus auratus) infected by Strongyloides venezuelensis at 43 days of age. However, Mimori et al. (1982) observed no alteration on the number of goblet cells in the intestine of rodents infected by S. ratti.

In the intestinal epithelium, goblet cells are responsible by production and excretion of mucines responsible for the  lubrication  and  protection against pathogens (Miller, 1987; Deplancke and Gaskins, 2001). Alterations in goblet cells and mucus constitution are observed in response to parasite and microorganisms infection (Deplancke and Gaskins, 2001; Banks et al., 2005; Lievin -le Moal and Servin, 2006), as well as the hyperplasia in response to helmints infection (Onah and Nawa, 2000) and the hypersecretion induced by enterotoxins from Escherichia coli and coleric toxin (Banks et al., 2005).

Dawkins et al. (1983), when studying R. novergicus infected by S. ratti, using electronic microscopy, observed that adult Strongillus remained between enterocytes. The Strongillus were in intimate proximity to these cells. The intestine epithelium cells were distorted, showing the action of these parasites on the intestinal mucosa, such organisms keep their presence in the jejunum mucosa, impairing nutrient absorption and being responsible by malabsorption syndrome.

In the present study the jejunum of rodents infected by Strongyloides spp. suffered alterations in the mucosa; it was found smaller villi length, greater crypt depth, and an increase in the number of goblet cells in the jejunum crypts. These morphofunctional alterations impair the absorption capacity of the intestine, consequently they may promote a reduction on the growth and physical development of the host animal.

The authors have not declared any conflict of interests.

The authors are grateful to all who contributed to the capture of the rodents and to UNIPAR for financing this research.