Ecological drivers of helminth infection patterns in the Virunga Massif mountain gorilla population.

The Virunga Massif mountain gorilla population has been periodically monitored since the early 1970s, with gradually increasing effort. The population declined drastically in the 1970s, but the numbers stabilized in the 1980s. Since then, the population has been steadily increasing within their limited habitat fragment that is surrounded by a dense human population. We examined fecal samples collected during the Virunga 2015-2016 surveys in monitored and unmonitored gorilla groups and quantified strongylid and tapeworm infections using egg counts per gram to determine environmental and host factors that shape these helminth infections. We showed that higher strongylid infections were present in gorilla groups with smaller size of the 500-m buffered minimum-convex polygon (MCP) of detected nest sites per gorilla group, but in higher gorilla densities and inhabiting vegetation types occurring at higher elevations with higher precipitation and lower temperatures. On the contrary, the impact of monitoring (habituation) was minor, detected in tapeworms and only when in the interaction with environmental variables and MCP area. Our results suggest that the Virunga mountain gorilla population may be partially regulated by strongylid nematodes at higher gorilla densities. New health challenges are probably emerging among mountain gorillas because of the success of conservation efforts, as manifested by significant increases in gorilla numbers in recent decades, but few possibilities for the population expansion due to limited amounts of habitat.

Fleas from domestic dogs and rodents in Rwanda carry Rickettsia asembonensis and Bartonella tribocorum.

Fleas (Siphonaptera) are ubiquitous blood-sucking parasites that transmit a range of vector-borne pathogens. The present study examined rodents (n = 29) and domestic dogs (n = 7) living in the vicinity of the Volcanoes National Park, Rwanda, for fleas, identified flea species from these hosts, and detected Bartonella (Rhizobiales: Bartonellaceae) and Rickettsia (Rickettsiales: Rickettsiaceae) DNA. The most frequently encountered flea on rodents was Xenopsylla brasiliensis (Siphonaptera: Pulicidae). In addition, Ctenophthalmus (Ethioctenophthalmus) calceatus cabirus (Siphonaptera: Hystrichopsyllidae) and Ctenocephalides felis strongylus (Siphonaptera: Pulicidae) were determined using morphology and sequencing of the cytochrome c oxidase subunit I and cytochrome c oxidase subunit II genes (cox1 and cox2, respectively). Bartonella tribocorum DNA was detected in X. brasiliensis and Rickettsia asembonensis DNA (a Rickettsia felis-like organism) was detected in C. felis strongylus. The present work complements studies that clarify the distributions of flea-borne pathogens and potential role of fleas in disease transmission in sub-Saharan Africa. In the context of high-density housing in central sub-Saharan Africa, the detection of B. tribocorum and R. asembonensis highlights the need for surveillance in both rural and urban areas to identify likely reservoirs.

Hyperkeratotic mange caused by Sarcoptes scabiei (Acariformes: Sarcoptidae) in juvenile human-habituated mountain gorillas (Gorilla gorilla beringei).

To facilitate ecotourism and behavioral research, free-ranging mountain gorillas (Gorilla gorilla beringei) have been habituated to humans. During routine health monitoring, five juvenile gorillas were observed with active crusted dermatitis and alopecia. Papular and vesicular lesions and crusts with papular eruption and oozing were numerous and disseminated over the body of one gorilla with a confirmed infestation of scabies. In this gorilla, the hyperkeratotic crusts were loose and thick with a flaky and scaly appearance. Histologically, the epidermis was thickened, displayed hyperkeratosis and was infiltrated with lymphocytes and neutrophils. Examination of skin scraping yielded a positive identification of adults and eggs of Sarcoptes scabiei mites. The gorillas were treated with ivermectin, 200 mg kg(-1). As S. scabiei mites can cross-infect various mammalian species causing self-limiting dermatitis, these ectoparasites can be propagated in the habitats shared by gorillas, people, and livestock, and therefore they represent an anthropozoonotic threat.

Field anesthesia of free-living mountain gorillas (Gorilla gorilla beringei) from the Virunga Volcano region, Central Africa.

Twenty-six anesthetic procedures involving 24 free-living mountain gorillas (Gorilla gorilla beringei) from Rwanda or the Democratic Republic of Congo were performed between February 1987 and October 1997. Sixteen procedures were performed to remove snares or to treat snare-related wounds, and four of the animals died without recovering consciousness because of their severe medical conditions. Ketamine was used for induction 19 times, tiletamine/zolazepam was used five times, and the agent was not recorded for two procedures. The mean (+/- SD) ketamine dosage for four animals of known weight was 7.1 +/- 0.9 mg/kg. All induction agents were delivered i.m. by remote injection, and mean induction times for ketamine and tiletamine/zolazepam were 5.5 +/- 2.6 min (n = 12) and 5.4 +/- 3.7 min (n = 5), respectively. Mean recovery times were significantly shorter with ketamine compared with tiletamine/zolazepam (42.0 +/- 24.9 min, n = 9 vs. 75.25 +/- 22.1 min, n = 4). Low hemoglobin oxygen saturation (mean = 86.7%) was recorded in three cases under ketamine anesthesia, and oxygen insufflation is therefore recommended to prevent hypoxemia. Gorillas induced with tiletamine/zolazepam had significantly higher respiratory rates compared with animals given ketamine. Successful anesthesia and recovery, in particular, depended on the assistance of local personnel.

Gastrointestinal parasites of mountain gorillas (Gorilla gorilla beringei) in the Parc National des Volcans, Rwanda.

Ninety-eight fecal samples were collected from 74 free-living mountain gorillas (Gorilla gorilla beringei) from the Parc National des Volcans, Rwanda, between July 1995 and January 1997 and examined for parasites by Sheather's sugar and zinc sulfate flotation methods, trichrome staining, and larval cultures. All samples contained at least one parasite. Seventeen endoparasites were identified, including eight protozoa, seven nematodes, one cestode, and one trematode. Two species of arthropod mite were also recovered from the fecal samples. Parasites observed on fecal examinations included strongyle/trichostrongyle-type eggs (72/74) (representing Oesphagostomum sp., Trichostrongylus sp., Hyostrongylus spp., and possibly Murshidia sp.), Strongyloides sp. (1/74), Trichuris trichiura (2/74), Probstmayria sp. (7/74), Anoplocephala sp. (63/74), Entamoeba hartmanni cysts and trophozoites (19/70), Endolimax nana cysts (31/70), Iodamoeba buetschlii cysts (11/70), Endolimax nana or Iodamoeba buetschlii trophozoites (63/70). Entamoeba coli cysts and trophozoites (14/70), Entamoeba histolytica trophozoite (1/70), Chilomastix sp. cysts and trophozoites (31/70), and Giardia sp. cysts (2/70). In addition, one ascarid and one trematode egg were seen. There were no significant differences in the prevalence of parasites between males and females and between age groups: however, infants and juveniles appeared to have a lower prevalence of Anoplocephala gorillae, and the silverbacked males appeared to have a higher prevalence of Probstmayria sp. Parasite prevalence was consistent among the five social groups studied except Susa group had a significantly lower prevalence of Anoplocephala gorillae. Trichuris trichiura, Strongyloides sp., Chilomastix sp., and Endolimax nana were identified for the first time in this population, and it is possible that these parasites were of human origin. Although there were no obvious clinical effects due to the presence of these parasites, six parasites identified (Trichuris trichiura, Strongyloides sp., Oesphagostomum sp., Trichostrongylus sp., Entamoeba histolytica, and Giardia sp.) could potentially be pathogenic. Some of the parasite products and cultured larvae could not be speciated.

Analysis of urine from free-ranging mountain gorillas (Gorilla gorilla beringei) for normal physiologic values.

Voided urine samples were collected from apparently healthy free-living mountain gorillas (Gorilla gorilla beringei) and analyzed for normal physiologic values. Mountain gorillas were found to have a high urinary pH (x = 8.45) and low specific gravity (x = 1.013). Commercial dipsticks appear to be unreliable for the measurement of specific gravity and leukocytes. The establishment of urinary reference intervals should aid in the noninvasive detection of certain diseases in the mountain gorilla and assist with prompt and effective decisions regarding the immobilization and treatment of individual gorillas.