Objective. To identify, describe and determine the frequency of species of the genus Eimeria from goat feces from the state of Nuevo Leon, Mexico. Materials and methods. From 403 samples of goat excreta from 13 municipalities of Nuevo Leon, Mexico. Subsequently, after sporulation of the parasite dispersal forms (Oocysts), identification was made according to their morphology and morphometry by means of histograms and linear regression analysis. Results. A total of 60.29% of the animals sampled were positive for the presence of oocysts of Eimeria spp. The municipalities in which this parasite was most frequently detected were Ramones and Pesquería with 100% of positive samples, while a lower frequency was observed in the municipality of Aramberri with 3.4%. The morphological and morphometric analysis of the sporulated oocysts allowed the identification of 8 different types of Eimeria in the group of animals studied: E. caprina, E. caprovina, E. christenseni, E. ninakohlyakimovae, E. jolchijevi, E. alijevi, E. arloingi and E. apsheronica. Conclusions. Most of the identified Eimeria spp. showed a high degree of polymorphism. According to their morphometric characteristics, eight species were identified, including E. apsheronica, which has not been previously described in Mexico. Further studies of Eimeria species circulating in goats in Mexico are required.

Goat production systems in northeastern Mexico are primarily extensive and semi-extensive farming systems on small farms located in semiarid regions. There is little or no modernization of livestock production processes. Overcrowding, excess humidity, and feces accumulation in pens create favorable environmental conditions for parasite development, increasing the risk of eimeriosis.

Parasitic diseases are a major cause of economic losses because they reduce overall production and predispose animals to secondary diseases, resulting in high mortality among young animals, especially stressed ones (1).

Eimeriosis is one of the gastrointestinal diseases with the greatest economic impact on goat farming (2). Eimeriosis can become a serious infection under intensive production conditions characterized by high productivity and animal density (3). Because young animals are the most vulnerable, good sanitation practices, especially in and around kidding areas, are critical for preventing clinical coccidiosis (4). Nevertheless, few studies on the species of coccidia that affect goats have been conducted. Several species of pathogens are known to be specific to these small ruminants. For example, Eimeria arloingi causes polyp formation and focal hyperplasia of the mucosa; E. ninakohlyakimovae and E. caprina damage the mucosa in the large and small intestines; E. christenseni and E. hirci have pathogenic capacity. These five species are likely to be the most pathogenic species (5,6).

Because of the significance of this parasitosis, different species of the genus Eimeria have been studied and identified in goats worldwide (7,8). There is scarce information on the diversity and prevalence of Eimeria species in Mexico, particularly in the state of Nuevo León (9). Therefore, the aim of this study was to describe and identify the species of this genus and to determine their frequency in goat feces.

Study site. The study was conducted in the state of Nuevo León, located in northeastern Mexico between 23º 11′ and 27º 49′ N latitude and 98º 26′ E and 101º 14′ W longitude. Nuevo León is divided into 51 local governmental units (municipalities) and has an area of 64,220 km., covering 3.3% of Mexico’s land area. It is bounded by Tamaulipas in the North and East, by the states of Zacatecas and San Luis Potosí in the West and South (10).

Population studied. Using random sampling, 403 fecal samples were collected directly from the rectum of 70 goat herds in 13 municipalities in Nuevo León, namely García, Iturbide, Aramberri, General Bravo, Marín, Galeana, Linares, Ramones, Pesquería, General Zuazua, Vallecillo, Cadereyta Jiménez, and Mina.

Laboratory methods. The samples were examined at the Parasitology Laboratory, School of Veterinary Medicine and Animal Husbandry, Universidad Autónoma de Nuevo León. The feces were macerated and placed in petri dishes containing 2.5% potassium dichromate (K.Cr.O.), followed by incubation at 23–28ºC. Each sample was monitored daily until 70% of the oocysts sporulated.

The oocysts were obtained by flotation using 37% zinc sulfate (371 g of ZnSO. in 1 L of distilled water) and saturated sugar solution (450 g of sugar in 355 mL of distilled water), as described by Foreyt (11).

Analysis of results. Morphological observations and measurements of the sporulated oocysts were performed using a Carl Zeiss Axioscope binocular microscope equipped with an AxioCam HRc camera and 40× and 100× lenses, as described by Berto et al. (12).

The observed values of the largest diameter, smallest diameter, and morphometric index of oocysts and their respective frequencies were analyzed via histograms and linear regressions using the software Microsoft. Excel. 2011 for Mac Version 14.4.6. (12).

Oocysts of Eimeria spp. were found in only 243 (60.29%) of the 403 animals sampled in the municipalities of García, Iturbide, Aramberri, General Bravo, Marín, Galeana, Linares, Ramones, Pesquería, General Zuazua, Vallecillo, Cadereyta Jiménez, and Mina.

The morphological and morphometric analyses revealed eight species of Eimeria that had not previously been reported in these municipalities in Nuevo León. Their frequency values were as follows: E. arloingi type 1, 24.57%; E. christenseni, 14.64%; E. alijevi, 11.41%; E. arloingi type 2, 10.17%; E. jolchijevi, 9.39%; E. caprovina, 8.93%; E. ninakohlyakimovae, 8.19%; E. caprina, 5.71%; and E. apsheronica, 5.21%. There were differences in the distribution of species per municipality. All of the species identified in this study were found in 6 of the 13 municipalities, namely Cadereyta Jiménez, Galeana, General Bravo, Mina, Pesquería, and Iturbide. Seven species were identified in García and Zuazua; six species in Marín and Ramones; five species in Vallecillo; two species in Linares; and only one species in Aramberri (Table 1). Multiple species were frequently found infecting a single host.

Different shapes and sizes were observed in the oocysts of the identified species. Based on the presence or absence of micropylar caps, the eight species were divided into two groups. E. arloingi types 1 and 2, E. jolchijevi, and E. christenseni had a micropylar cap (Figure 1), whereas the cap was absent in E. alijevi, E. ninakohlyakimovae, E. apsheronica, E. caprina, andE. caprovina (Figure 2).

Table 1. Prevalence of Eimeria species by municipality in Nuevo León, Mexico.

Eimeria arloingi Marotel, 1905

Two morphological patterns were observed in this species. In type 1, the oocysts were ellipsoidal, sometimes ovoid, and measured 26.3–32.0 (29.1) × 18.2–23.9 (20.9) µm (Figure 1). In type 2, the oocysts were ellipsoidal, occasionally slightly sub-spherical, and measured 24.1–27.9 (25.9) × 18.2–22.2 (20.2) µm (Figure 1). The bilayered wall measured 1.64–1.55 µm. A micropyle was present, with a rounded micropylar cap (MC) on top. One to several large polar granules (PGs) were present, with one to two being the most common. The oocyst residuum (OR) was absent; the sporocysts were ellipsoidal; the Stieda body (SB) was flattened; and both sub-SB (SSB) and para-SB (PSB) were absent. The sporocyst residuum (SR) is composed of small granules that cross almost all the sporocysts. Each sporozoite had two refractile bodies (RBs). The histograms for this species showed gradually ascending and descending frequencies, indicating the presence of a single species with two types.

Eimeria jolchijevi Musaev, 1979

E. jolchijevi oocysts were ellipsoidal in shape, measuring 29.8–35.2 (32.1) × 19.6–30 (22.9) μm (Figure 1). The bilayered wall measured 1.52 μm, with an evident micropyle. The MC measured 1.72 × 7 μm, was translucent, and varied in shape. Many small PGs were observed, and there could be several large ones. Ellipsoidal sporocysts and the OR were absent. Flattened SB, SSB, and PSB were absent. The SR was composed of large granules that were scattered along the sporocyst; however, the SR can also be more compact. Two RBs per sporozoite were observed. They were present near the center of the sporocyst and were close to each other. The characteristics of the RBs are as follows: a larger dark RB and a slightly smaller transparent RB, with a dark spot in the center of the small RB at times. The histograms for this species showed a tendency for the frequencies to gradually increase and decrease, indicating that the minimum and maximum values are lower than the mid values. This, therefore, indicates that the oocysts measured are from a single species.

Eimeria christenseni Levine, 1962

The oocysts were characterized as ovoid ellipsoidal and measured 32.9–43.3 (37.9) × 22.4–28.2 (25.4) μm (Figure 1). Bilayered wall measuring 1.90 μm and dark brown in color. Micropyle present. MC translucent and prominent measuring 2.02 × 7.69 μm. One to several large PGs, more frequently only one, with dense and very refractile appearance. Sprocytes were ellipsoidal in shape. OR, SSB, and PSB were absent. SR was composed of granules of different sizes and very refractile. Three RBs were present—a dark one at each end of the sporozoite and a colorless one between them. One of the RBs at the extremes is always located at the bottom of the SB. In the histogram for this species, the frequencies in the classes tended to increase and decrease gradually, so that the smallest and largest oocyst sizes occurred in smaller numbers at the lower and upper limits of the histogram, indicating that it was a single species. The morphometric index (MI) values for all classes >1.1, indicating that the species was ellipsoidal. Most of the oocysts showed MI values between 1.45–1.5.

Eimeria alijevi Mausaev, 1970

The oocysts of this species were most commonly ellipsoidal; however, spherical or sub-spherical oocysts could also be found, measuring 16–22.9 (20.3) × 14.4–20.5 (17.7) μm (Figure 2). Bilayered wall with micropyle present measuring 1.59 and 2.77 μm, respectively. PG present. MC and SR absent. Ellipsoidal sporocysts with small, flattened SB. SSB and PSB absent. Little SR. Two RBs per sporozoite. E. alijevi had a micropyle, although not always very evident, and in all cases presented SB. The histogram analysis showed that it was a single species.

Eimeria ninakohlyakimovae Yakimoff and Rastegaieff, 1930

The oocysts were typically ellipsoidal–sometimes spherical and sub-spherical–and measured 18.6–26.4 (23.8) × 17.3- 22.9 (19.9) μm (Figure 2). Bilayered wall measuring approximately 2.04 μm. Micropyle present, MC absent. One to several PGs. No OR, SSB, or PSB observed. The sporocysts were ellipsoidal, small, and bottle or lemon shaped. With distinct, flattened, and small SB. SR rather compact composed of small granules of regular size. Two RBs per sporozoite. The histograms for this species showed a tendency for frequencies to gradually increase and decrease. Such tendencies were between 19.5 and 20.6 (smallest diameter, [SD]), 23.3 and 24.9 (largest diameter [LD]), and 1.10 and 1.20 (MI). The presence of a single peak in each histogram shows that this was a single species.

Eimeria apsheronica Musaev, 1970

The oocysts were characterized as ovoid ellipsoidal and measured 30.8–34.6 (23.7) × 21.3–25.1 (23.7) μm (Figure 2). Bilayered wall measuring 1.82 μm, dark brown in color. Narrow micropyle measuring 3.51 μm without MC. One to several large and several small PGs. OR absent. Drop-shaped ellipsoidal sporocysts. Flattened SB, SSB, and PSB absent. SR with very small and uniform granules. Two RBs per sporozoite—one dark and one lighter—of the same size. From the histograms for this species, LD and SD showed a gradual increase and decrease in frequencies, with most of them between 32.3–33.1 and between 23.6–24.6 respectively, which indicates that the measured oocysts belonged to a single species.

Eimeria caprina Lima, 1980

The oocysts were typically ellipsoidal, sometimes sub-spherical, and measured 26.1–36 (27.7) × 20.12–26.53 (23.7) μm (Figure 2). Bilayered wall measuring approximately 1.44 μm. Micropyle measuring 3.96 μm without MC with many and very small PGs and no evidence of OR. Ellipsoidal sporocysts, with very pronounced bottle shape. SB flattened and conspicuous and absence of SSB and PSB. Two RBs per sporozoite one larger than the other sometimes a dark spot was observed behind the larger one. From the histograms for this species, LD and SD showed a gradual increase and decrease in frequencies, with most of them between 31.4 and 33 μm and between 24 and 25.2 (23.7), respectively, which indicates that the measured oocysts belonged to a single species.

Eimeria caprovina Lima, 1980

The oocysts were ellipsoidal and measured 25.4–30.5 (27.7) × 19.3–23 (21.2) μm. (Figure 2). Bilayered wall measuring 1.99 μm. Micropyle measuring 2.85 μm without MC. One to three PGs, no OR observed. Ellipsoidal sporocysts. SB small and flattened. CSC and PSB absemt. Little SR, more conspicuously observable as lines on the sides of the sporocyst like small granules. Two RBs per sporozoite—one darker than the other. The histograms showed a regular distribution with the highest frequencies between 27.4 and 28.4 μm (LD) and between 20.8 and 21.5 (SD). The frequencies increased and decreased gradually, thus indicating that the measured oocysts belonged to a single species.

Coccidia in sheep and goats are host-specific, and there is no cross infection (5). The Eimeria species infesting these animals have long been considered identical based on their morphology, which explains the great confusion that can be found in previously published studies on the different species of Eimeria in small ruminants (13). Nevertheless, it has been shown that some species considered as parasites of goats and sheep were not able to infect one or the other of these hosts in cross-transmission studies (3).

Proper identification of the coccidia species is essential to determine the species distribution of this important parasite.

The prevalence of goat eimeriosis depends on complex interactions between the parasite and its host, as well as on various factors that affect the severity of this parasitosis, such as the age of the animal, stress, genetic susceptibility, physical condition, and degree of immunity, among others (14). The species identified in this study have been reported worldwide with different prevalence values, such as 100% in Ukraine, 98.6% in southern Portugal, 96.7% in the state of Punjab in India, 92.2% in the Czech Republic, 89.2% in Malaysia, 80.75% in Nepal, 76% in Poland, 60% in Egypt, 54% in northern Jordan, and 42.2% in Iraq (15). The frequency found in this research was 60.29%.

Of the 16 species of Eimeria that have been described in goats from different parts of the world, E. christenseni, E. arloingi, E. caprina, and E. ninakohlyakimovae are the species with the highest pathogenicity (3, 16).

Based on our results, E. arloingi showed the highest prevalence in the study area, which is similar to that observed in other countries such as Australia, Poland, Kenya, the Netherlands, Tanzania, the Czech Republic, South Africa, Turkey (14), China (17), and the United States (16).

Likewise,E. arloingi was shown to be the most prevalent species in Myanmar through morphological and molecular studies (18) and in Senegal, Nigeria, Zimbabwe (18), and India (19) through microscopic examination.

In this study, the highly pathogenic E. ninakohlyakimovae and E. caprina (6) showed low frequency values (8.19 and 5.71%, respectively).

Six of the seven Eimeria species identified in goats in Egypt coincided with the species found in our study, namely E. caprina, E. ninakohlyakimovae, E. jolchijevi, E. christenseni, E. arloingi, and E. apsheronica. In addition, we identified E. caprovina and E. alijevi, whereas E. hirci was reported in Egypt. The species most frequently found in Egyptian goats were E. hirci (24.69%), E. ninakohlyakimovae (30.86%), and E. arloingi (37.04%). The latter was the most prevalent species in both cases, with a value of 24.57% in our study (20).

The georeferencing of the location and occurrence of the genus Eimeria spp. in several animal species including goats, from 1961 to 2018, was recently published in Mexico. Eight species were reported in this document, namely E. alijevi, E. arloingi, E. caprina, E. caprovina, E. christenseni, E. hirci, E. jolchijevi, and E. ninakohlyakimovae (9). It should be noted that E. apsheronica is not documented, and therefore this would be the first report of its presence in goats in Mexico.

Finally, this work aims to provide information on the species of coccidia present in goats in northeastern Mexico.

We conclude that the frequency of caprine eimeriosis in the state of Nuevo León, Mexico, is 60.29% and parasitized goats were found in all the municipalities sampled. Eight species were described according to their morphology and morphometry, namely E. caprina, E. caprovina, E. christenseni,E. ninakohlyakimovae, E. jolchijevi, E. apsheronica, E. alijevi, and E. arloingi. The most prevalent species in this state were E. arloingi type 1 (24.57%) and E. christenseni (14.64%). On the other hand, the least frequent species was E. apsheronica (5.21%), and this would be the first record of this species in Mexico.

The authors declare that there are no potential conflicts of interest with respect to the research or authorship of this article.