Diphenyl diselenide modulates nucleotidases, reducing inflammatory responses in the liver of Toxoplasma gondii-infected mice.

The aim of this study was to verify the effect of diphenyl diselenide (PhSe)2 on hepatic nucleotidases and on the concentration of purines in mice infected by Toxoplasma gondii. The animals were divided into four groups: Group A (uninfected), Group B (uninfected and treated with (PhSe)2), Group C (infected), and Group D (infected and treated with (PhSe)2). The inoculation (groups C and D) was performed with 50 cysts of T. gondii (ME-49 strain). Mice from groups B and D were treated with 5 µmol kg-1 of (PhSe)2. Liver tissue from infected mice showed less severe inflammation, elevated ATP/ADO ratio, elevated NTPDase, 5'nucleotidase, and ADA activities compared to the uninfected group (Group A; P < 0.05). However, infected and treated mice showed decreased ATP levels and elevated ADO levels, as well as higher NTPDase and 5'nucleotidase activities and decreased ADA activity in the hepatic tissue compared to the infected group (P < 0.05). Moreover, the (PhSe)2 treatment of infected mice reduced the hepatic inflammation and showed an immunomodulatory effect on ectonucleotidases of hepatic lymphocytes, which it returned to basal levels. Therefore, chronic infection by T. gondii induces hepatic inflammation in mice, and it is possible that purine levels and nucleotidase activities in hepatic tissue are related to the pathogenesis of the infection in this tissue. The treatment with (PhSe)2 was able to reverse the hepatic inflammation in mice chronically infected, possibly due to the modulation of purinergic enzymes that produce an anti-inflammatory profile through the purinergic system in the liver tissue.

Risk factors for Neospora caninum infection in dairy cattle and their possible cause-effect relation for disease.

Neospora caninum causes reproductive problems in cattle such as abortion, premature birth, retention of fetal membranes, and metritis. Therefore, this study aimed to verify possible risk factors for N. caninum infection in dairy cattle and their cause-effect relation to neosporosis. Serum samples of 1518 dairy cows from the West of Santa Catarina State, Southern Brazil were analyzed by indirect immunofluorescence assay (IFA) for N. caninum, where 466 were found to be positives (30.69%-CI95%; 28.3-33.0). In addition, an epidemiological survey was conducted in order to verify possible risk factors for neosporosis and their relation to the disease. The presence of dogs in the farm was strongly associated with IFA positive results for N. caninum, and lack of history for neosporosis in the farm increased the chances of positivity in 66%. It was found a significant cause-effect relation between the occurrence of reproductive problems and the presence of antibodies against N. caninum (p = 0.05). It is possible to conclude that N. caninum is widely distributed in dairy farms of the Western part of Santa Catarina state, Brazil, and that the occurrence of reproductive problems is directly related to the disease with the presence of dogs as a risk factor for N. caninum infection.

Toxoplasmosis treatment with diphenyl diselenide in infected mice modulates the activity of purinergic enzymes and reduces inflammation in spleen.

Toxoplasma gondii, an intracellular protozoan, may cause chronic infection in the brain tissue of the host inducing a systemic pro-inflammatory profile. Chronic infections can induce numerous physiological changes, such as alterations in the immune and oxidative profiles. Diphenyl diselenide (PhSe)2, an organoselenium compound, has shown antioxidant and immunomodulatory activities in recent studies. So, the aim of this study was to investigate the activity of purinergic enzymes and reactive oxygen species (ROS) in serum and spleen of mice chronically infected by T. gondii, untreated and treated with (PhSe)2. For this experiment, were divided into four groups: Group A (healthy mice), Group B (healthy mice treated with (PhSe)2), Group C (infected mice) and Group D (infected mice treated with (PhSe)2). Group C and group D were infected via oral route with ME49 Toxoplasma gondii strain. Groups B and D were treated subcutaneously with 5 µmol kg-1 of (PhSe)2. Chronic T. gondii infection induced splenomegaly and physiological changes in the spleen and raised histologic inflammatory markers, ROS levels and the activity of purinergic enzymes activity such as NTPDase, 5´nucleotidase and ADA. In serum, the infection increased 5´nucleotidase and ADA activities. (PhSe)2per se has managed to decrease ROS levels and ADA activity and increase NTPDase and 5´nucleotidase in spleen. In infected mice, treatment with (PhSe)2 reversed splenomegaly, reduced histological inflammatory markers, ROS levels and ADA activity in the spleen. Our results prove that chronic toxoplasmosis can induce splenomegaly, heightens ROS levels and purinergic enzyme activity in mice. These results suggest that (PhSe)2 is a potential therapy for the alterations found in the spleen in chronic T. gondii infection.

Hepatic xanthine oxidase activity and purine nucleosides levels as physiological mediators to analyze a subcutaneous treatment with (PhSe)2 in mice infected by Toxoplasma gondii.

The aim of this study was to evaluate the levels of purine nucleosides and xanthine oxidase (XO) activity in the liver of mice chronically infected by Toxoplasma gondii and treated with diphenyl diselenide (PhSe)2. For this experiment, forty Swiss mice were used. Twenty animals were orally infected by approximately 50 bradizoites of a cystogenic ME-49 strain of T. gondii, and the same number of uninfected mice was used as a control group. Ten infected and ten uninfected mice were subcutaneously treated twice (days 1 and 20 post-infection (PI)) with 5 µmol kg-1 of (PhSe)2. On day 30 PI, liver samples were collected to measure the levels of hypoxanthine (HYPO), xanthine (XAN), uric acid (UA), and XO activity. Infected animals showed increased (P < 0.05) levels of hepatic XAN and UA, as well as XO activity compared to uninfected animals. The use of (PhSe)2 in healthy mice increased the levels of all nucleosides, but decreased XO activity compared to healthy untreated animals. The group of infected and treated animals showed increased XAN and UA levels, and XO activity compared to the healthy control group, however infected and treated mice showed a decrease in the XO activity compared to the infected untreated group. We conclude that chronic infection caused by T. gondii can induce hepatic changes, such as increased UA levels and XO activity, that can increase the pro-oxidative profile. The (PhSe)2 treatment of healthy animals altered the levels of nucleosides, possibly due to low XO activity that decreased nucleoside degradation. Finally, (PhSe)2 treatment decreased XO activity in the infected group and increased nucleoside levels; however it was unable to reduce the UA levels found during the infection.

Toxoplasma gondii infection in dairy ewes: Vertical transmission and influence on milk production and reproductive performance.

The present study aimed to evaluate the transmission of toxoplasmosis (vertical and venereal) and its influence on milk production and reproductive problems of Lacaune sheep seropositives for Toxoplasma gondii. Males and females were serologically selected using indirect immunofluorescence method in three steps of the study. Step 1: In order to evaluate the influence of toxoplasmosis on milk production, the volume of milk produced by 40 sheep (22 seronegatives and 18 seropositives for T. gondii) was weekly measured throughout the lactation period. There were no significant differences between these two groups; in other words, toxoplasmosis did not affect milk production. Step 2: In order to assess T. gondii venereal transmission, five samples of semen from seropositive rams (n = 5) were tested by endpoint and real time PCR with two days of interval; however, these semen samples were PCR negatives for T. gondii. Step 3: To evaluate reproductive problems, 12 seropositive animals out of a flock of 68 pregnant ewes showed signs of reproductive problems, such as abortion or fetal resorption. T. gondii transplacental transmission was evaluated on blood drawn from newborn lambs (n = 41), and their respective seropositive mothers (n = 30) after single, double or triple births. Serological tests showed that 65.8% of the lambs had antibodies against this protozoan, indicating a high transmission from ewe to fetus during pregnancy. Therefore, it is concluded that toxoplasmosis in sheep may impair reproduction with a high percentage of vertical transmission.

Horses seropositive for Toxoplasma gondii, Sarcocystis spp. and Neospora spp.: Possible risk factors for infection in Brazil.

Many parasitic diseases are considered asymptomatic, even though some studies have shown that they may cause pathological changes in the host. Therefore, the aim of this study was to evaluate the occurrence of antibodies against Toxoplasma gondii, Neospora spp. and Sarcocystis spp. in horses, and to identify the risk factors for disease. For this, 174 horses were studied, 90 males and 84 females aged between two and 20 years old. Blood samples were collected and stored in tubes without anticoagulant to obtain serum, which was subjected to serological tests for T. gondii, Sarcocystis spp., and Neospora spp. using indirect immunofluorescence assay (IFA). IFA results were as follows: Sarcocystis spp. 41.37% (72/174) (CI95%-34.05-49.09); T. gondii 32.18% (56/174) (CI95%-25.42-39.74) and Neospora spp. 48.27% (84/174) (CI95%-40.68.50-55.93). Out of 174 horses, 81 had simple infection, 61 had mixed infections with two or three of these pathogens, and therefore, only 32 horses showed no antibodies to any of these pathogens. No risk factors for Sarcocystis spp. and T. gondii infection were identified. However, there was a significant (1.22-CI95%-1.02-1.52) relationship between animal age and Neospora spp. infection, since older animals showed higher prevalence. Therefore, it was possible to conclude that T. gondii and Neospora spp. affect horses in Southern Brazil, however all the animals studied were asymptomatic without reproductive, neurological or locomotor problems.

Diphenyl diselenide supplementation in infected mice by Toxoplasma gondii: Protective effect on behavior, neuromodulation and oxidative stress caused by disease.

The aim of this study was to evaluate the effect of subcutaneous administration of diphenyl diselenide (PhSe)2 on animal behavior and activities of acetylcholinesterase (AChE), adenylate kinase (AK), and creatine kinase (CK) in the brain of mice infected by Toxoplasma gondii. In addition, thiobarbituric acid reactive species (TBARS) levels and glutathione (GR, GPx and GST) activity were also evaluated. For the study, 40 female mice were divided into four groups of 10 animals each: group A (uninfected and untreated), group B (uninfected and treated with (PhSe)2), group C (infected and untreated) and group D (infected and treated with (PhSe)2). The mice were inoculated with 50 cysts of the ME49 strain of T. gondii. After infection the animals of the groups B and D were treated on days 1 and 20 post-infection (PI) with 5.0 µmol/kg of (PhSe)2 subcutaneously. Behavioral tests were conducted on days 29 PI to assess memory loss (object recognition), anxiety (elevated plus maze), locomotor and exploratory activity (Open Field) and it was found out that infected and untreated animals (group C) had developed anxiety and memory impairment, and the (PhSe)2 treatment did not reverse these behavioral changes on infected animals treated with (PhSe)2 (group D). The results showed an increase on AChE activity (P < 0.01) in the brain of infected and untreated animals (group C) compared to the uninfected and untreated animals (group A). The AK and CK activities decreased in infected and untreated animals (group C) compared to the uninfected and untreated animals (group A) (P < 0.01), however the (PhSe)2 treatment did not reverse these alterations. Infected and untreated animals (group C) showed increased TBARS levels and GR activity, and decreased GPx and GST activities when compared to uninfected and untreated animals (group A). Infected animals treated with (PhSe)2 (group D) decreased TBARS levels and GR activity, while increased GST activity when compared to infected and untreated animals (group C). It was concluded that (PhSe)2 showed antioxidant activity, but the dose used had no anti-inflammatory effect and failed to reverse the behavioral changes caused by the parasite.

Toxoplasma gondii: Effects of diphenyl diselenide in experimental toxoplasmosis on biomarkers of cardiac function.

This study aimed to investigate the effects of diphenyl diselenide (PhSe)2 to treat mice experimentally infected by Toxoplasma gondii on seric biomarkers of cardiac function (creatine kinase, creatine kinase MB, troponin, and myoglobin), and lactate dehydrogenase, as well as to evaluate the enzymatic activity of creatine kinase (CK) and adenylate kinase (AK) in heart tissue. For the study, 40 female mice were divided into four groups of 10 animals each: the group A (uninfected and untreated), the group B (uninfected and treated), the group C (infected and untreated) and the group D (infected and treated). The inoculation was performed with 50 cysts of T. gondii (ME-49 strain). Mice from groups B and D were treated at days 1 and 20 post-infection (PI) with 5 µmol kg(-1) of (PhSe)2 subcutaneously. On day 30 PI, the mice were anesthetized and euthanized for blood and heart collection. As a result, it was observed a decrease in AK activity (P < 0.01) in the heart samples of groups C and D compared to the group A. Cardiac CK increased in the group C compared to the group A (P < 0.01). CK levels increased in infected mice (the group C) compared to other groups (A and D). Regarding CK-MB level, there was a decrease in the group D compared to the group B, without statistical difference compared to control groups (A and C). It was observed an increase on myoglobin in groups C and D, differently of troponin, which did not show statistical difference (P < 0.05) between groups. Mice from the group C showed an increase in lactate dehydrogenase (LDH) levels compared to other groups (A, B, and D). Histopathological evaluation of heart samples revealed necrosis, hemorrhagic regions and inflammatory infiltrates in mice from the Group C, differently from the group D where animals showed only inflammatory infiltrates. Based on these results we conclude that the (PhSe)2 had a protective effect on the heart in experimental toxoplasmosis by modulating tissue and seric CK activity, and avoiding an increase on seric LDH levels, probably due to the antioxidant effect of this compound.

Synergistic effects of resveratrol (free and inclusion complex) and sulfamethoxazole-trimetropim treatment on pathology, oxidant/antioxidant status and behavior of mice infected with Toxoplasma gondii.

This study aimed to investigate the synergistic effects of resveratrol and sulfamethoxazole-trimethoprim (ST) on the treatment of mice experimentally infected by Toxoplasma gondii during the chronic phase of the disease considering infection, behavior, and oxidative/antioxidants profile aspects. For the study, 60 mice were initially divided into two groups: uninfected (n = 24) and infected by T. gondii (n = 36). These two groups were later subdivided into other groups and treated with resveratrol (free and inclusion complex containing resveratrol) alone and co-administered with ST: groups A to D were composed by healthy mice and groups E to J were consisted of animals infected by T. gondii (VEG strain). Treatments began 20 days post-infection for 10 consecutive days with oral doses of 0.5 mg kg(-1) of ST (groups B and F), 100 mg kg(-1) of free resveratrol (groups C and G) and inclusion complex of resveratrol (nanoparticles containing resveratrol) (groups D and H), and lastly an co-administration of both drugs (groups I and J). Behavioral tests (memory, anxiety and locomotion) were performed after treatment. Liver and brain fragments were collected to evaluate pathological changes, brain cysts counts, as well as oxidant and antioxidant levels. A reduction on the number of cysts in the brain of animals treated with both drugs combined was observed; there was also reduced number of lesions on both organs. This drug combined effect was also able to reduce oxidative and increase antioxidant levels in infected mice, which might be interpreted as a resveratrol protective effect. In addition, the combination of ST and resveratrol was able to prevent behavioral changes in infected mice. Therefore, the use of co-administration drugs enhances the therapeutic effect acting on a synergic way, reducing the oxidizing effects of the chemical treatment for toxoplasmosis. In addition, resveratrol in inclusion complex when co-administered with ST showed an improved therapeutic effect of ST reducing oxidative damage, liver damage and the number of cysts in the brain of T. gondii infected mice.

Relation between Neospora caninum and abortion in dairy cows: Risk factors and pathogenesis of disease.

Neosporosis is a parasitic disease cause by Neospora caninum, a parasite of great importance in livestock. This study aimed to evaluate the presence of antibody against N. caninum in dairy cattle with history of abortion, as well as to identify associated risk factors for neosporosis. Animals suspected of neosporosis (n = 130) after clinical examination were randomly selected. Sera samples from 29 farms were submitted to indirect immunofluorescence technique (IFA) in order to detect antibodies against N. caninum, and animals were considered positive if ≥ IFA 1:200. An epidemiological questionnaire was used to verify probable risk factors for neosporosis and their cause-effect relation. Serological results showed that 43.8% of the animals were seropositives for N. caninum. The univariate statistical analysis found a significant relation between neoporosis and age. The number of pregnancies and the number of years that the farms had been producing milk were found as associated risk factors for the disease either by univariate or by multivariate analyses. The cause-effect model found a possible relation between reproductive problems and positive serology for neosporosis (P = 0.06). Therefore, it was concluded that approximately 44% of dairy cows with history of abortion were seropositives for N. caninum and that age and the number of years that the farms had been producing milk are risk factors for parasite infection in dairy cattle.

Effects of sulfamethoxazole-trimethoprim associated to resveratrol on its free form and complexed with 2-hydroxypropyl-ß-cyclodextrin on cytokines levels of mice infected by Toxoplasma gondii.

The aim of this study was to investigate the effects of resveratrol on its free form and complexed with 2-hydroxypropyl-ß-cyclodextrin (HPßCD) when associated with sulfamethoxazole-trimethoprim (ST) on cytokines levels of mice (n = 60) experimentally infected by Toxoplasma gondii. Groups A and E were used as controls (untreated): negative and positive, respectively. The onset of treatment started 20 days post-infection (PI), and it lasted for 10 consecutive days. ST was administered orally in doses of 0.5 mg kg(-1) for groups B and F, while 100 mg kg(-1) was the dose for resveratrol in its free form (groups C - G), inclusion complex (groups D and H), and on free and inclusion complex together (groups I - J). On day 31 PI, blood samples were collected in order to evaluate the cytokine profile. The mice that received drug combination (I and J) showed a significant (P < 0.05) reduction in the number of cysts in the brain compared to other infected groups (E - H). The results showed that mice from the Group E had increased (P < 0.001) levels of pro-inflammatory cytokines, while IL-10 levels were reduced when compared to the Group A. Additionally, there were increased levels of IL-4 and IFN-γ in animals of groups C and D, respectively (P < 0.05). Animals of the Group B showed reduced levels of IL-1, IL-4, IL-6, TNF-α, and IFN-γ (P < 0.05). Mice infected and treated (groups F - J) showed increased levels of pro-inflammatory cytokines along with a reduction of IL-10. Treatment with the combination of drugs (the Group J) led to a protective effect, i.e. reduction in pro-inflammatory cytokines. Therefore, resveratrol associated with ST was able to modulate seric cytokine profile and moderate the tissue inflammatory process caused by T. gondii infection, as well as to reduce parasite multiplication.

Sulfamethoxazole-trimethoprim associated with resveratrol for the treatment of toxoplasmosis in mice: Influence on the activity of enzymes involved in brain neurotransmission.

This study aimed to investigate the influence of sulfamethoxazole-trimethoprim (ST) associated with resveratrol on the enzymatic activities of acetylcholinesterase (AChE), adenylate kinase (AK), pyruvate kinase (PK), and creatine kinase (CK) in the brain of mice experimentally infected by Toxoplasma gondii. For that, 60 mice were divided into ten groups with 6 animals each: groups A to D composed by healthy mice and groups E to J consisting of animals infected by T. gondii (VEG strain). Animals started treatment 20 days post-infection for 10 consecutive days with oral doses of 0.5 mg kg(-1) of ST (groups B and F), 100 mg kg(-1) of free resveratrol (groups C and G) and inclusion complex of resveratrol (nanoparticles containing resveratrol) (groups D and H), as well as with an association of both drugs (groups I and J). The results showed increased (P < 0.001) AChE activity on infected animals (groups E-J) when compared to not-infected (A) animals, and also uninfected animals treated with ST (group B) had increased AChE activity. AK activity decreased (P < 0.001) in the infected and untreated (group E), differently from the other groups that did not differ. PK activity did not differ between groups (P > 0.05). When comparing control groups (uninfected (A) and infected (E)), we verified a significant (P < 0.001) increase in CK activity in the brain, and it is noteworthy that the animals treated with resveratrol associated with ST (group I and J) had similar CK activity to those animals from the group A. Treatment with the combination of ST and resveratrol was able to reduce (P < 0.05) the number of parasitic cysts in the brain, thus reduced inflammatory infiltrates in the liver, and prevented the occurrence of hepatocytes lesions due to toxoplasmosis in mice. Based on these results, it is possible to conclude that increased AChE and CK activities after T. gondii infection did not change with the treatment of ST-resveratrol association. In addition, decreased AK activity caused by T. gondii infection was normalized by ST-resveratrol treatment. T. gondii infection and treatment does not affect PK activity in brain.

Diphenyl diselenide and sodium selenite associated with chemotherapy in experimental toxoplasmosis: influence on oxidant/antioxidant biomarkers and cytokine modulation.

SUMMARY The aim of this study was to assess the effect of sulfamethoxazole/trimethoprim (ST) supplemented with diphenyl diselenide and sodium selenite in experimental toxoplasmosis, on oxidant/antioxidant biomarkers and cytokine levels. Eighty-four BALB/c mice were divided in seven groups: group A (negative control), and groups B to G (infected). Blood and liver samples were collected on days 4 and 20 post infection (p.i.). Levels of thiobarbituric acid (TBA) reactive substances and advanced oxidation protein products (AOPP) were assessed in liver samples. Both biomarkers were significantly increased in infected groups on day 4 p.i., while they were reduced on day 20 p.i., compared with group A. Glutathione reductase (GR) activity significantly (P<0·01) increased on day 4 p.i., in group G, compared with group A. INF-γ was significantly increased (P<0·001) in both periods, day 4 (groups B, C, F and G) and 20 p.i. (groups C, F and G). IL-10 significantly reduced (P<0·001) on day 4 p.i. in group B; however, in the same period, it was increased (P<0·001) in groups C and G, compared with group A. On day 20 p.i., IL-10 increased (P<0·001) in groups F and G. Therefore, our results highlighted that these forms of selenium, associated with the chemotherapy, were able to reduce lipid peroxidation and protein oxidation, providing a beneficial immunological balance between the production of pro- and anti-inflammatory cytokines.

Changes in purine levels associated with cellular brain injury in gerbils experimentally infected with Neospora caninum.

The present study was carried out in order to assess the possible alterations in purine levels of brain, associated neuronal lesions in gerbils experimentally infected with Neospora caninum. For that, gerbils (Meriones unguiculatus) were inoculated with Nc-1 strain of N. caninum, composing two different experiments: Experiment I (EI) and experiment II (EII), where purine levels were measured along with the histopathologic study, on days 7 (EI), 15 and 30 (EII), post-infection (PI). As a result, it was possible to observe that the purine levels (ATP, ADP, AMP, adenosine, inosine and xanthine) in brain in EI are significantly reduced (p < 0.05), while in EII we faced a different pattern, since in the majority the purine levels were significantly increased (p < 0.05) on days 15 (ATP, AMP, adenosine, hypoxanthine and xanthine) and 30 PI (ATP, ADP, AMP, adenosine, and uric acid). Results of brain histopathology did not show histological lesion in animals of EI; however, in gerbils of EII it was possible to verify that the alterations (lesions) were more pronounced in gerbils evaluated on day 30 PI when compared to day 15 PI. Therefore, it was possible to conclude that the purine levels in brain were altered in both experiments, concomitant with the histopathological injuries observed in EII.

Oxidative stress in brain tissue of gerbils experimentally infected with Neospora caninum.

Neospora caninum infection is generally latent and asymptomatic, and it results in the formation of dormant encysted bradyzoites that remain in the brain and other tissues of infected animals for life, causing major economic and pathological problems. The aim of this study was to assess the relation between infection by N. caninum and its damage to brain tissue through the evaluation of biomarkers of oxidative stress during the acute and chronic phases of the disease. Sixteen gerbil (Meriones unguiculatus) were divided into 3 groups: Group A (n = 6) was composed of healthy animals, while group B (n = 5) was infected with 0.1 ml containing 2.5 × 10(6) tachyzoites of N. caninum in order to achieve the acute phase, and, finally, group C (n = 5) was infected with a lower dose (0.1 ml containing 5 × 10(4)) of N. caninum tachyzoites in order to produce the chronic phase of the disease. All evaluations were performed on brain tissue on days 7 and 30 postinfection (PI), with assessment of the levels of several biomarkers of oxidative stress, including nitrate/nitrite (NOx), lipid peroxidation (TBARS), protein oxidation (AOPP), and activity of glutathione reductase (GR). Brain levels of TBARS and AOPP statistically differed (P < 0.05) among the 3 groups when compared to the control group, since both biomarkers showed reduced levels on day 7 PI, and increased levels on day 30 PI. Brain activity of GR increased significantly in animals from group C when compared to groups A and B. On day 7 PI, histological lesions and parasites in the brain were not observed, whereas in the chronic phase group, the infected gerbils (day 30 PI) showed areas of inflammatory infiltrate, accompanied by the presence of the parasite in the brain. These results suggest that the oxidative stress occurs at both time points, but the patterns of the biomarkers are different.

Neospora caninum: Activity of cholinesterases during the acute and chronic phases of an experimental infection in gerbils.

Neosporosis is an infectious disease primarily of dogs and cattle which has been found in many countries around the world. Neospora caninum causes an important immune response (cellular and humoral) in animals that it infects. Since the participation of the cholinergic system in the immune response is well documented, the aim of this study was to evaluate the relationship between N. caninum infection and activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) during the acute and chronic phase of infection. For that, tachyzoites of N. caninum (Nc-1 strain) were inoculated intraperitoneally in gerbils (Meriones unguiculatus), which were separated in two experiments, I and II, differing in infective doses of tachyzoites, aiming to reach an acute phase as well as chronic phase, respectively. Samples were collected on day 7 post infection (PI) for Experiment I and on days 15 and 30 PI for Experiment II. AChE activity was evaluated on whole blood and brain, while BChE was evaluated in plasma. On day 7 a reduction of AChE in total blood and brain was observed, along with reduction of BChE in plasma of infected animals when compared with non-infected. In Experiment II, AChE activity increased in total blood on day 30 PI; however, maintaining, during the same period, the AChE activity has a reduced in brain tissue. BChE activity was significantly increased on day 30 PI. Based on the results obtained, it was possible to observe a response of the cholinergic system, providing different grades of AChE and BChE activities, in response to the acute and chronic infection of gerbils experimentally infected with N. caninum. These results will serve as initial points to further studies of our research group about the relationship between the infection/disease and the cholinergic system.