In Antioquia, the problems to control Rhipicephalus microplus (Canestrini, 1888) tick infestations have spread and ranchers claim conventional treatments are no longer effective. In this study, the in vitro efficacy of commercial topical products was tested with ticks obtained from two dairy farms in Antioquia with severe repeated infestations. About 800 engorged ticks were collected directly from animals in two separate visits at the beginning and end of the same month. The adult immersion test was used, which exposed groups of 40 ticks from each collection at the recommended concentration for five commercial products and combinations for 5 min. Efficacy was determined by comparing the reproductive index (fecundity × fertility) of each treated group to that of the control group. The values of all reproductive parameters obtained with ticks from the two collection dates were very similar. Cypermethrin (150 ppm) and amitraz (208 ppm) separately showed very low efficacies of only 10-20% at one farm, and zero at the other. The combination of chlorpyrifos + cypermethrin was the only product with an efficacy >50% at both farms and field observations corroborated to be still capable of eliminating infestations. Exposure to fluazuron at concentrations ranging from 0.05 to 500 ppm for 1 min reduced fertility in all groups by ≥99%, as would be expected for very susceptible strains. However, reduction of oviposition only occurred at the 500 ppm concentration. In conclusion, there is a high degree of resistance to all products tested except for fluazuron.

Two distant Antioquian cattle farms where systemic and topical acaricides had previously failed to control infestations by Rhipicephalus (Boophilus) microplus were studied. An initial in vivo study was conducted using single subcutaneous injections with a long-acting formulation of ivermectin (630 μg/kg). Injections were made at 3-month intervals on animals at each farm to evaluate the therapeutic and persistent efficacy of ivermectin against R. microplus. Body tick counts and reproductive parameters of semi- or fully engorged females (≥5 mm) were assessed at 10-day intervals, and since no negative control group could be included, values were compared against those for day 0. Although there was an overall reduction of 50%–75% in tick numbers that persisted for 30–40 days, it was not significantly different at one of the farms and not enough to afford protection from severe infestations. The engorgement weight and egg mass weight of ticks from treated animals were significantly lower throughout the 50-day posttreatment period. Egg hatch was not significantly reduced posttreatment and remained at levels of 80%–90%. A random selection of 9 out of 28 commercial formulations of ivermectin sold in Colombia were analyzed by High Performance Liquid Chromatography (HPLC). All were within the expected labeled concentration (±15% deviation) of 1% and 3.15% ivermectin except for one. A popular unregistered injectable widely used in both farms and labeled as “natural pyrethrin”, was found to contain 10.5% ivermectin. An adult immersion test was conducted to evaluate the efficacy of topical acaricides to recommended concentrations of five commercial products and/or their combinations. Efficacy was determined by comparing the reproductive index of each treated group to that of the control group. Cypermethrin (150 ppm) was completely ineffective at both farms. Amitraz (208 ppm) exhibited low and intermediate efficacies of 14% and 56%. The combination of amitraz (100 ppm) and cypermethrin (150 ppm) was less efficacious than the amitraz alone. A generic product based on amitraz + citronella (208 ppm + 10 ppm, respectively) was shown to be less efficacious than the name-brand amitraz product. Products containing the organophosphate chlorpyrifos or trichlorfon exhibited intermediate efficacies of approximately 60% at the Tarso farm. We conclude that at these two locations, there is a high degree of resistance to many of the acaricides available in Colombia and confirm suspicions that ivermectin is no longer able to eliminate tick infestations.

Parasitic agents are a common cause of diarrhea in dogs and cats and, thus, determining their prevalence is essential to establish preventive and control measures. This retrospective study examined the fecal tests records from 1111 dogs and 203 cats with diarrhea submitted to a diagnostic laboratory in the city of Medellin between January and May 2018. The detection of parasites was carried out by direct smears and simple flotation methods. Parasitic organisms were detected in feces from 464 (41.7%) dogs and 96 (47.3%) cats. In order of decreasing prevalence, the parasites detected in dogs were: Giardia intestinalis (13%), ancylostomids (12.6%), Entamoeba spp. (6.1%), coccidian oocysts (5.8%), Toxocara spp. (5.6%) and Dipylidium caninum (1.3%). In cats, the prevalence was: Giardia intestinalis (20%), coccidian oocysts (8.9%), Entamoeba spp. (7.9%), ancylostomids (6.4%), Toxocara spp. (2.5%) and Dipylidium caninum (2%). Age, but not gender, was a predisposing factor, as puppies and kittens had significantly higher infection rates that older age categories. The majority of Giardia intestinalis positive cases occurred in puppies (109/145, 75.2%) and kittens (19/36, 52.8%), making this parasite the most prevalent in amongst animals with diarrhea. Out of 117 positive infections in the adult dog population, ancylostomids accounted for 56 cases (47.9%) and was the most common parasite in this age group. In conclusion, although these results do not imply a cause and effect relationship, they are an estimate of the type of parasites that may be most commonly associated with diarrhea in dogs and cats. The lower diagnostic sensitivity of the traditional methods used here as compared to more contemporary techniques like fecal flotation with centrifugation and PCR, may have underestimated the actual prevalence and diminished the detection of coinfections. Future studies should aim to have diagnostic panels that also screen for other enteric pathogens, including bacterial and viral agents.

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