Canine Monocytic Ehrlichiosis (CME) is an infectious disease caused by the rickettsia organism Ehrlichia canis which is transmitted mainly the ixodid brown dog tick Rhipicephalus sanguineus . The prevalence of E. canis infection has been increasing in recent years. The World Health Organization has been warned about antibiotics resistance and one of the way to prevent this situation is found new compound with this property. Doxycycline is the treatment of choice for this tick-borne disease. Adverse effects are noted in dogs that are sensitive to this drug. Antibiotic resistance may also occur. The present study aimed to evaluate the anti- Ehrlichia properties of the essential oil of the aerial parts of Ageratum conyzoides L. in infected DH82 cells, as well as its anti- Ehrlichia activity associated with doxycycline using the checkerboard assay. A. conyzoides is a native plant from northeast Brazil with many reports of ethnopharmacological applications. The essential oil of A. conyzoides was extracted from the aerial parts of the plant using the hydrodistillation method. E. canis -infected DH82 cells were cultured in DMEM (Dulbecco’s Modified Eagle Medium), maintained at 37 °C and 5% CO 2 , and standardized at a 70% infection rate for the initiation of treatment protocols. The tests were first carried out with the aim of defining the IC 50 . The combined effect of doxycycline and A. conyzoides essential oil was then determined using the checkerboard dilution technique (checkerboard method) in which the IC 50 was 200 µg/mL. The doxycycline reduction index from the combined effect was 4.90 times resulting in a synergistic effect. To the authors’ knowledge, this is the first alternative treatment (alternative therapy) based on bioactive molecules that have antibacterial activity against E. canis .

Ehrlichia canis is an intracellular bacterium that infects hematopoietic cells. It is the causative agent of canine monocytic ehrlichiosis (CME). The disease may be acute, subclinical, or chronic, and is treated with tetracyclines including doxycycline. However, this class of tetracyclines may cause several side effects due to prolonged treatment. Bacterial resistance to antimicrobials has been extensively reported. The present study aimed to assess the anti- Ehrlichia activity of the dichloromethane extract (DCM) of Ageratum conyzoides L. on Ehrlichia- infected DH82 cells. For this purpose, the DCM extract of A. conyzoides collected in the municipality of São Luís, State of Maranhão (MA), northeast Brazil, was obtained from the aerial parts of the plant by exhaustive percolation in H 2 O- CH 2 Cl 2 (2:8) and subsequent extraction of the chemical compound. The chemical composition of these samples was investigated. The anti- Ehrlichia properties of A. conyzoides were confirmed in Ehrlichia- infected DH82 cells at a concentration of 200 μg.mL -1 of its DCM extract. The results of the treatments were evaluated at 18h and 36h after the insertion of the treatments evaluated with A. conyzoides.Based on the results of the chemical analysis of the samples, we may attribute these antirickettsial properties to the compounds from the lignan family that are found in this medicinal plant .

Mycoplasma suis is a bacterium that causes hemoplasmosis in pigs. This agent is capable of adhering to the surface of porcine erythrocytes, inducing structural changes on these cells. In Brazil, there are few reports about the disease, its causal agent, and the economic impact of this pathogen on pig production systems and farm sanitation. The present study aimed to investigate the occurrence of M. suis in extensive swine farms located in the counties of Itapecuru Mirim, Santa Rita and Rosario, State of Maranhão, northeast Brazil. For such purpose, 64 blood samples of pigs from these facilities were tested for M. suis using a 16S rRNA gene-based quantitative real-time PCR (qPCR); 82.3%, 65.2% and 25% of blood samples of swine from farms in the cities of Itapecuru Mirim, Santa Rita and Rosario were positive for M. suis by qPCR, respectively. This study shows, for the first time, that M. suis circulates in pig populations from the state of Maranhão, Northeast Brazil.

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