Mitochondrial genetic diversity, selection and recombination in a canine transmissible cancer

Canine transmissible venereal tumour (CTVT) is a clonally transmissible cancer that originated approximately 11,000 years ago and affects dogs worldwide. Despite the clonal origin of the CTVT nuclear genome, CTVT mitochondrial genomes (mtDNAs) have been acquired by periodic capture from transient hosts. We sequenced 449 complete mtDNAs from a global population of CTVTs, and show that mtDNA horizontal transfer has occurred at least five times, delineating five tumour clades whose distributions track two millennia of dog global migration. Negative selection has operated to prevent accumulation of deleterious mutations in captured mtDNA, and recombination has caused occasional mtDNA re-assortment. These findings implicate functional mtDNA as a driver of CTVT global metastatic spread, further highlighting the important role of mtDNA in cancer evolution.

DOI:http://dx.doi.org/10.7554/eLife.14552.001

A unique cancer called canine transmissible venereal tumour (CTVT) causes ugly tumours to form on the genitals of dogs. Unlike most other cancers, CTVT is contagious: the cancer cells can be directly transferred from one dog to another when they mate. The disease originated from the cancer cells of one individual dog that lived approximately 11,000 years ago. CTVT now affects dogs all over the world, which makes it the oldest and most widespread cancer known in nature.

Like healthy cells, cancer cells contain compartments known as mitochondria that produce the chemical energy needed to power vital processes. Inside the mitochondria, there is some DNA that encodes the proteins that mitochondria need to perform this role. Changes (or mutations) to this mitochondrial DNA (mtDNA) may stop the mitochondria from working properly. CTVT cells have previously been found to occasionally capture mtDNA from normal dog cells, which suggests that replenishing their mtDNA may help promote CTVT cell growth. Furthermore, these captured mtDNAs act as genetic "flags" that can help trace the spread of the disease.

Here, Strakova, Ní Leathlobhair et al. analysed the mtDNA in CTVT tumours collected from over 400 dogs in 39 countries. The analysis shows that CTVT cells have captured mtDNA from normal dog cells on at least five occasions. Over the last 2,000 years, the disease appears to have spread rapidly around the world, perhaps transported by dogs travelling on ships along historic trade routes. CTVT may have only reached the Americas within the last 500 years, possibly carried there by dogs brought by Europeans. Likewise, CTVT probably only came to Australia after European contact.

The experiments also revealed that the most damaging types of mutations were absent from the mtDNA of CTVT, which suggests that fully functioning mitochondria play an important role in CTVT. Unexpectedly, Strakova, Ní Leathlobhair et al. found evidence that certain sections of mtDNA in some CTVT cells have been exchanged, or shuffled, with the mtDNA captured from normal dog cells. This type of “recombination” is not usually thought to occur in mtDNA, and has not previously been detected in cancer. Future studies will determine if this process is widespread in other types of cancer, including in humans.

DOI:http://dx.doi.org/10.7554/eLife.14552.002

Somatic evolution and global expansion of an ancient transmissible cancer lineage

The canine transmissible venereal tumor (CTVT) is a cancer lineage that arose several millennia ago and survives by "metastasizing" between hosts through cell transfer. The somatic mutations in this cancer record its phylogeography and evolutionary history. We constructed a time-resolved phylogeny from 546 CTVT exomes and describe the lineage's worldwide expansion. Examining variation in mutational exposure, we identify a highly context-specific mutational process that operated early in the cancer's evolution but subsequently vanished, correlate ultraviolet-light mutagenesis with tumor latitude, and describe tumors with heritable hyperactivity of an endogenous mutational process. CTVT displays little evidence of ongoing positive selection, and negative selection is detectable only in essential genes. We illustrate how long-lived clonal organisms capture changing mutagenic environments, and reveal that neutral genetic drift is the dominant feature of long-term cancer evolution.

Plant products and secondary metabolites with acaricide activity against ticks

The present review documents the results of studies evaluating the acaricidal activity of different plant products and secondary metabolites against ticks that are resistant and susceptible to conventional acaricides. Studies published from 1998 to 2016 were included. The acaricidal activity of plant extracts, essential oils and secondary compounds from plants have been evaluated using bioassays with ticks in the larval and adult stages. There is variable effectiveness according to the species of plant and the concentrations used, with observed mortalities ranging from 5 to 100% against the Rhipicephalus (Boophilus), Amblyomma, Dermacentor, Hyalomma, and Argas genera. A number of plants have been reported to cause high mortalities and/or affect the reproductive capacity of ticks in the adult phase. In the majority of these trials, the main species of plants evaluated correspond to the families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae. Different secondary metabolites such as thymol, carvacrol, 1,8-cineol and n-hexanal, have been found to be primarily responsible for the acaricidal activity of different essential oils against different species of ticks, while nicotine, dibenzyldisulfide and dibenzyltrisulfide have been evaluated for plant extracts. Only thymol, carvacrol and 1,8-cineol have been evaluated for acaricidal activity under in vivo conditions. The information in the present review allows the conclusion that the secondary metabolites contained in plant products could be used as an alternative for the control of ticks that are susceptible or resistant to commercial acaricides.

American trypanosomiasis in dogs from an urban and rural area of Yucatan, Mexico

American trypanosomiasis in dogs is reported from South of the United States to Argentina and Chile. It is transmitted through the contact of dogs with reduviid insects when they feed; reduviid insects are well established in the southern state of Yucatan, Mexico. However, there are no reports available about trypanosomiasis prevalence in dogs of urban and rural areas. A cross-sectional study was performed in 345 stray dogs, 102 from a rural community of Yucatan (Tunkas) and 243 from Merida, capital city of the Yucatan state. Serum samples were obtained for detection of immunoglobulin G antibodies against Trypanosoma cruzi by indirect immunofluorescence assay and Western blot. DNA was extracted from whole blood of urban dogs for polymerase chain reaction (PCR) assay. Prevalence was determined and the risk to become infected in both urban and rural dogs was evaluated using a 2 x 2 contingency table. In addition to the effect of body condition score (BCS), the age and sex of dogs were also evaluated to determine the risk of infection. Antibody prevalence against T. cruzi in rural areas was 9.8%, whereas in urban dogs was 14.4%. When PCR results were included, prevalence in dogs from the urban area increased to 17.3%. PCR allowed the detection of active asymptomatic acute-phase disease. The risk to become infected was not different between urban and rural areas, suggesting that the vector is well adapted both to rural areas and urban sprawling. Dogs with poor BCS tended to have a higher probability of seroreactivity to T. cruzi proteins than dogs with regular or good BCS (p = 0.05).

Serological survey of American trypanosomiasis in dogs and their owners from an urban area of Mérida Yucatàn, México

American trypanosomiasis is an important zoonotic disease which affects more than 15 million persons in America. In Mexico, Chagas' disease is widely distributed in the country mostly in states with tropical weather conditions, including Yucatan. A cross-sectional study was performed on serum samples from 35 dogs and their owners (n = 75) from the south area of Merida city. Specific IgG antibodies against Trypanosoma cruzi (T. cruzi) using enzyme-linked immunosorbent assay, Immunofluorescence antibody test (IFI) and Western blot (WB) were detected. The overall percentage of seropositivity was 34% in dogs and 8% for sampled owners. Some owners brought samples of insect vectors found in their households, which were kept with BALB/c mice as a source of food and which were evaluated by polymerase chain reaction. All tested insects were positive to T. cruzi, and BALB/C mice were IFI and WB positive after 45 days in contact with these vectors. Further investigations showed that there is a high risk of infection with Chagas disease in dogs which spend the night outdoors (P < 0.05), with low body conditions score and older dogs. Risk factors identified to be associated to the infection in owners were gender and occupation (bricklayers, P < 0.05). The presence of seropositive dogs in houses where vectors are well-adapted represents a high risk for humans to become infected when bitten by a vector infected by a positive dog.

Reproductive patterns and reproductive pathologies of stray bitches in the tropics

The objectives of this study were to determine the annual reproductive pattern and to estimate the frequency of reproductive pathologies in female mongrel stray dogs under tropical conditions. The genital tracts of 300 mongrel bitches from a municipal dog pound were examined post-mortem from January to December 2003. Season of the year, age, size, and body condition score (BCS) were recorded for each dog. The year was divided into three seasons: warm-dry (March-June), warm-humid (July-October), and fresh-humid (November-February). Distribution of estrus periods was not influenced by any of the factors studied (i.e. season, age, size, BCS). A significantly lower number of pregnancies were recorded during the warm-dry season, probably as a consequence of embryo resorption. Underweight animals had a significantly lower percentage of pregnancies than bitches of ideal BCS. More ovulations per bitch occurred during the warm-humid season than during the other seasons of the year, probably due to climatic factors. Bitches of medium and large size had more ovulations than those of small size. Of the 300 bitches examined, 43.5% had one or more genital pathologies. The most frequent pathologies found in the ovary, uterus, and vagina were epoöphoron cysts (6.7%), serosal inclusion cysts (5.0%), and transmissible venereal tumors (15.3%), but the capacity of the females to come into estrus or to become pregnant was not affected by these conditions. We concluded that stray domestic bitches in the tropics were not seasonal breeders, but their reproductive pattern was apparently modified by environmental factors such as temperature and probably photoperiod. Although several bitches in the present study had reproductive pathology, the most prevalent pathologies did not adversely reproductive capacity.

Factors affecting the prevalence of mange-mite infestations in stray dogs of Yucatán, Mexico

The aim of the present study was to determine the factors affecting the prevalence of mange-mite infestations in stray dogs of Yucatán, Mexico. The study was carried out in 200 stray dogs of Mérida capital city of Yucatán, Mexico. Four samples (head, thoracic-abdominal area, extremities and ear) were taken from each animal by skin scraping and examined microscopically in 10% KOH solution to detect the presence of mites. Mites were also collected from the external ear canal of dogs using cotton-tipped swabs. The prevalence of different mite species was calculated. A primary screening was performed using 2xK contingency tables of exposure variables. All variables with P< or =0.20 were analyzed by a logistic-binomial regression. The overall prevalence was 34%. Demodex canis (23.0%) was the most frequent mite, followed by Sarcoptes scabei var. canis (7.0%) and Otodectes cynotis (3.5%). The following factors were found: body condition (bad, OR: 5.35, CI 95%: 1.66-17.3; regular, OR: 3.72, CI 95%: 1.39-9.99) and the presence of macroscopic lesions of dermatosis (OR: 42.80, CI 95%: 13.65-134.24).

Pathological Conditions of the Reproductive Organs of Male Stray Dogs in the Tropics: Prevalence, Risk Factors, Morphological Findings and Testosterone Concentrations

The objective of this study was to estimate the prevalence of and risk factors for pathological conditions of the reproductive organs in stray dogs under tropical conditions. Three hundred and eighteen dogs were examined post-mortem in the period from 1 July 2002 to 30 June 2003. Before killing, a blood sample (from the cephalic vein) for testosterone assay was taken. Pathological conditions of the reproductive organs were found in 135 of the dogs (42.5%) and in 175 of the testes (64.8%). The most frequent pathologies found were testicular degeneration, cryptorchidism, testicular hypoplasia and testicular tumours (in 15.1%, 6.6%, 6.6% and 5.4% of the dogs and 15.1, 4.6, 6.0 and 3.5 of the testes, respectively). Transmissible venereal tumour (TVT) was seen in 5.4% of the dogs. Testicular degeneration was more common in old dogs and underweight dogs (p < 0.05). Testicular tumours were 14.3 times more common in cryptorchid dogs. Age was another important factor for the development of testicular tumours (p < 0.05). Lower levels of testosterone concentration (p < 0.05) were observed in dogs with advanced testicular degeneration (0.7 +/- 0.8 nM), dogs with hypoplastic testicles (0.8 +/- 0.9 nM) and dogs with one degenerated and one retained testis or with bilateral cryptorchidism (1.2 +/- 0.9 nM) compared to dogs with one or two normal testes (7.0 +/- 5.5 nM). Testicular volume and weight were significantly lower in degenerated, hypoplastic and retained testes compared with the contralateral normal testis. Some spermatogenic activity was found in three of the retained testes, producing oligozoospermic smears with a high percentage of sperm abnormalities. No comparable epidemiological data about male pathological conditions of the reproductive organs in the dog is available. The prevalence found in this study, yet, appears high.

Prevalence and Risk Factors of Toxoplasma gondii Infection in Domestic Cats from the Tropics of Mexico Using Serological and Molecular Tests

The aim of this study was to determine the prevalence and risk factors associated with Toxoplasma gondii infection in domestic cats using an indirect-ELISA (IgM and IgG) and PCR. Samples collected from 220 cats from Merida, Yucatan, Mexico, were analyzed. Cases were reported as acute or chronic. Cases when positive to IgM and IgG and PCR were considered as reactivated chronic infection. Risk factors (sex, age, body condition, diet access to hunting, and number of cats in home) were assessed with a multivariate analysis, 75.5% (166/220) of the cats were IgM and 91.8% (202/220) IgG-seropositive and 79% were PCR-positive (173/220). Number of cats per household and low body condition score were associated with reactivated chronic infection (P < 0.05). It is concluded that T. gondii is scattered in the studied population with several periods of reinfection, and therefore an environmental contamination with infecting oocysts exists and there are intrinsic associated factors in cats that increase the risk of becoming infected.

Toxoplasmosis in Mexico: epidemiological situation in humans and animals

Toxoplasmosis is a parasitic disease widely distributed throughout the world, infecting a wide variety of animal species including humans. In Mexico, this parasite has been detected in different parts of the country, particularly in the tropical areas where the parasite can remain infective for long periods of time due to the environmental conditions (i.e. high temperature and humidity over the whole year). Several epidemiological studies have been conducted in both human and animal populations, but despite the wide distribution of the agent in the country, there is a significant lack of knowledge on the parasite transmission, treatment alternatives and control measures. The lack of feral cat populations and control measures in sites of meat production for human consumption are playing a role that has led to the wide spread of the disease in the country, particularly in tropical areas of Southeastern Mexico. For these reasons, this manuscript aims to review the published information on relevant epidemiological aspects of infection with T. gondii in humans and animals from Mexico.

Prevalence of the Dirofilaria immitis infection in dogs from Merida, Yucatan, Mexico

The aim of the present study was to estimate the prevalence of Dirofilaria immitis infection, and to examine the relationship between host factors (gender, age and breed) and D. immitis infection in dogs. The study was designed as a cross-sectional study. A total of 676 dogs were examined for D. immitis infection. Adult worms (necropsy) and blood samples were collected from all animals for diagnosis of D. immitis. Blood samples were examined using a modified Knott's and thick drop techniques. Fifty-six of 676 dogs were diagnosed infected with D. immitis. The odds of infection were 2.85 times higher in female dogs, compared to male dogs (OR = 2.85, 95% CI = 1.5-5.5, P = 0.01). In addition, the odds of infection were 2.11 times higher in > or =3 years old dogs, compared with younger dogs (OR = 2.11, 95% CI = 1.1-4.2, P = 0.03). This information is important for a better understanding of the epidemiology of D. immitis in dogs in Yucatan, Mexico.

Efficacy of Recombinase Polymerase Amplification to Diagnose Trypanosoma cruzi Infection in Dogs with Cardiac Alterations from an Endemic Area of Mexico

Chagas disease is a lingering Public Health problem in Latin America with ∼5.7 million people infected with Trypanosoma cruzi. Transmission is still taking place in most countries of the Americas, including the United States. Dogs are frequently infected with T. cruzi and its high infection prevalence is associated with increased risk of Chagas disease in humans. The city of Mérida in the Yucatan peninsula is endemic for Chagas disease and canines are frequently infected with T. cruzi. The objective of this study was to evaluate the performance of a qualitative point of care (POC) molecular test (RPA-LF, recombinase polymerase amplification-lateral flow) developed in our laboratory for identifying infected dogs. We used retrospective samples of dogs that came for consultation because of cardiac alterations and proved to be infected with T. cruzi as determined by enzyme-linked immunosorbent assay (ELISA), Western blot, and quantitative PCR (qPCR). The analytical sensitivity indicated that RPA-LF amplified T. cruzi DNA in samples containing almost equal to one to two parasites per reaction. Serial twofold dilutions of T. cruzi epimastigotes showed that the test had 95% (19/20) repeatability at concentrations of two parasites per reaction. The test showed no cross reactivity with human DNA or other protozoan parasites (Trypanosoma rangeli, Leishmania spp., and Plasmodium spp.). RPA-LF had the capacity to amplify all discrete typing units (DTUs I-VI) of T. cruzi that circulate in domestic or extradomestic environments. The RPA-LF had 93.2% (95% confidence interval 87.2-98.1) sensitivity and excellent agreement with qPCR used as gold standard (Cohen's Kappa test = 0.963). ELISA was positive in 96.6% (85/88) of dogs, which together with the molecular tests confirmed the frequent contact with infected triatomine bugs in the city of Mérida. These preliminary results on the diagnostic efficacy of the RPA-LF deserve further large-scale field testing of this POC test for T. cruzi infection in endemic areas.

Serological survey of canine leptospirosis in the tropics of Yucatan Mexico using two different tests

Blood samples were taken from 400 stray dogs. The microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA) test were implemented using Leptospira interrogans serogroups canicola, hardjo, pyrogenes, panama, pomona, tarassovi, icterohaemorrhagiae, gryppotyphosa, wolffi and brastislava. For the ELISA test, sonicated antigen from above mentioned cultures was used. A conjugate AP-labeled anti-dog IgG antibody was used, the optimal cut-off point of ELISA was set at 1.34. Concordance between ELISA and MAT titers was measured by kappa (kappa). Overall prevalence was 35%. The most prevalent serogroups were canicola and icterohaemorrhagiae. Positive samples showed titers between 1:100 and 1:25,600, with higher titers found in serogroups canicola and icterohaemorrhagiae. Positive serum samples fell within a range of 1.36-1.65. A correlation index of 96% was found between MAT and ELISA. The sensitivity of ELISA was 98.6% and specificity 95.8%. Seroprevalence of canine leptospirosis and titers were high as a direct consequence of environmental conditions in the studied area. The ELISA test showed a good sensitivity, resulting in a good alternative test for the detection of leptospiral antibodies in dog serum.

Seroprevalence of feline leukemia virus, feline immunodeficiency virus and heartworm infection among owned cats in tropical Mexico

Several infectious agents may be distributed within a healthy population of cats where diverse risk factors predispose them to come into contact with pathogens. Blood samples from 227 owned cats in Merida, Mexico, were collected with the objective of determining the seroprevalence and associated risk factors of feline leukemia virus (FeLV) and Dirofilaria immitis antigen, and feline immunodeficiency virus (FIV) antibody. Serological detection of FeLV and D immitis antigens, and FIV antibodies was performed using the commercial kit SNAP Feline Triple Test. The prevalence was found to be 7.5% for FeLV, 2.5% for FIV and 0% for D immitis. Adult cats were at a higher risk of coming into contact with FeLV (P <0.01) than younger cats. Owing to its low prevalence, a risk factor analysis was not performed for FIV. The prevalence of retroviral infections found in this study was low, but within the limits reported in the different geographical areas of the world. Cases of filariosis in the domestic cats of Merida, Mexico, may be absent or very low; however, the low sample size may have influenced these results.

Reproductive patterns of stray male dogs in the tropics

Two studies were performed to determine annual reproductive patterns in stray male dogs in the tropics. In Study 1, four dogs housed individually outdoors were monitored once monthly for 12 months, including collection and assessment of semen, measurements of scrotal width, and determination of serum testosterone and prolactin concentrations. In Study 2 (conducted concurrently), a single blood sample (for serum testosterone concentration) was collected from 220 clinically healthy dogs, and after euthanasia, scrotal width and morphology of epididymal sperm were determined. The year was divided into three seasons: warm-dry (March to June); warm-humid (July to October) and fresh-humid (November to February). In Study 1, scrotal width, ejaculate volume, sperm count and motility were significantly lower during the fresh-humid season and sperm midpiece abnormalities were significantly more common during the warm-humid and fresh-humid seasons. Serum testosterone concentrations remained constant during the year. Prolactin concentrations did not differ significantly among seasons, but had a well-defined increase from the beginning of March to the end of August. In Study 2, sperm morphology was similar to in Study 1 and serum testosterone concentrations varied nonsignificantly during the year. Environmental factors, e.g. daylength may have influenced circannual changes in prolactin secretion. Seasonal variations in some reproductive tract and seminal traits were significant but of small magnitude and the percentage of morphologically normal sperm did not vary significantly among seasons. In conclusion, healthy male dogs constantly produced sperm and were apparently fertile throughout the year.

Epidemiological survey of Trypanosoma cruzi infection in domestic owned cats from the tropical southeast of Mexico

American trypanosomiasis is an infectious disease of importance for public health and caused by the protozoa Trypanosoma cruzi mainly transmitted by triatomine bugs. The precise role of cats in the peridomestic transmission of T. cruzi and the mechanism by which cats become infected remain uncertain. The objective of this work was to determine the prevalence of T. cruzi infection in domestic cats from an urban area of tropical Mexico by serological and molecular methods and evaluate associated risk factors. A total of 220 domestic cats from Merida Yucatan, Mexico, were studied. Animals older than 3 months were blood sampled. Serum and DNA were obtained. Specific T. cruzi IgG antibodies were detected using a commercial indirect ELISA with an anti-cat antibody HRP labelled. Positive cases were confirmed by Western blot (WB). Polymerase chain reaction (PCR) was also performed using the primers TC1 and TC2. From the 220 cats, 8.6% had antibodies against T. cruzi using ELISA test and later confirmed by WB. In 75 cats (34%), the sequence of ADNk of T. cruzi was amplified. The bad-regular body condition was the only risk factor associated with PCR positive to T.cruzi (P < 0.001). In Mexico, there are no previous epidemiological reports that demonstrate the importance of the cat as a reservoir of T. cruzi. Few individuals were identified with a serological response because they were probably at an early stage of infection or antibodies were not detected because they could be immunocompromised (FIV, FeLV or others). It is necessary to monitor PCR-positive patients and conduct further studies for better understanding of the epidemiology and pathogenesis of Chagas disease in domestic cats.

Presence of Toxoplasma gondii in Drinking Water from an Endemic Region in Southern Mexico

Toxoplasmosis can be acquired through the ingestion of contaminated drinking water with oocysts of Toxoplasma gondii, highly resistant to the routinely disinfection processes; based on chlorination commonly used in the water supply industry. The aim of this study was to determine the presence of T. gondii DNA in samples of public drinking water from an endemic region of southern Mexico. In total 74 samples of water (5 L each) were collected from the three well fields (I, II, and III) and 71 independent wells, distributing public drinking water to the city of Merida Yucatan, after passing through the chlorination process. Water samples were filtered and concentrated by a sucrose solution, then DNA was extracted and evaluated through a nested-PCR (nPCR) specific for T. gondii. Positive samples were detected in 5.4% (4/74) of the water samples. This is the first report of the presence of T. gondii DNA in public drinking water from a large city in southern Mexico, where their consumption without any postpurification treatment could pose a risk for acquiring the infection in the urban population.

Biodiversity and distribution of helminths and protozoa in naturally infected horses from the biosphere reserve La Sierra Madre de Chiapas", México

A cross sectional survey was performed to identify gastrointestinal helminths and protozoans in naturally infected horses from the biosphere reserve known as "La Sierra Madre de Chiapas", Mexico (El Triunfo and La Sepultura). During a three-year survey, fecal samples from 90 horses and parasites from 2 necropsied animals were collected. Five families from the Nematoda class: Ascaridae, Kathlanidae, Oxyuridae, Strongylidae and Trichostrongylidae were found, whereas, only one family from the class Cestoda, was observed: Anoplocephalidae. One family from the class Insecta, was observed: Gasterophiilidae. The number of species of parasites ranged from 13 to 18 with an average of 15 per animal. Adult parasites were recovered from the large intestine luminal contents at necropsy. Species recovered included: Strongylus vulgaris, S. equinus, S. edentatus, Oxyuris equi, Parascaris equorum, Coronocyclus coronatum, C. labiatus, C. labratus, Cyathostomum tetracanthum, Cylicocyclus insigne, C. leptostomus, Cylicodontophorus bicoronatus, Cylicostephanus asymetricus, C. bidentatus, C. minutus, C. longibursatus, Petrovinema poculatum, Poteriostomum imparidentatum, Cylicostephanus goldi, Tridentoinfundibulum gobi, Triodontophorus serratus and T. tenuicollis. One species of Diptera were recovered from stomach and identified: Gasterophilus intestinalis. Furthermore, different species of protozoa were recovered from fresh horse-dung and identified in four classes: Sporozoa, Litostomatea, Ciliasida and Suctoria. Nine families: Cryptosporidiidae, Eimeriidae, Balantidiidae, Buetschliidae, Blepharocorythidae, Cycloposthiidae, Spirodiniididae, Ditoxidae, Acinetidae; and 31 ciliates species were recorded: Allantosoma dicorniger, A. intestinalis, Alloiozona trizona, Blepharosphaera intestinalis, Blepharoprosthium pireum, Blepharoconus benbrooki, Bundleia postciliata, Didesmis ovalis, D. quadrata, Sulcoarcus pellucidulus, Blepharocorys angusta, B. cardionucleata, B. curvigula, B. juvata, B. uncinata, B. valvata, Cycloposthium bipalmatum, C. edentatum, C. scutigerum, Charonina equi, Ditoxum funinucleum, Spirodinium equi, Tetratoxum unifasciculatum, Triadinium caudatum, T. galea, T. minimum and Tripalmaria dogieli. Other ciliate observed and recorded was Ochoterenaia appendiculata. This study describes the biodiversity and distribution of common and new helminths and protozoas found in the gastrointestinal tract from horses in the biosphere reserve "Sierra Madre de Chiapas" in Mexico.