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.

The evolutionary history of ACE2 usage within the coronavirus subgenus Sarbecovirus.

Severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) and SARS-CoV-2 are not phylogenetically closely related; however, both use the angiotensin-converting enzyme 2 (ACE2) receptor in humans for cell entry. This is not a universal sarbecovirus trait; for example, many known sarbecoviruses related to SARS-CoV-1 have two deletions in the receptor binding domain of the spike protein that render them incapable of using human ACE2. Here, we report three sequences of a novel sarbecovirus from Rwanda and Uganda that are phylogenetically intermediate to SARS-CoV-1 and SARS-CoV-2 and demonstrate via in vitro studies that they are also unable to utilize human ACE2. Furthermore, we show that the observed pattern of ACE2 usage among sarbecoviruses is best explained by recombination not of SARS-CoV-2, but of SARS-CoV-1 and its relatives. We show that the lineage that includes SARS-CoV-2 is most likely the ancestral ACE2-using lineage, and that recombination with at least one virus from this group conferred ACE2 usage to the lineage including SARS-CoV-1 at some time in the past. We argue that alternative scenarios such as convergent evolution are much less parsimonious; we show that biogeography and patterns of host tropism support the plausibility of a recombination scenario, and we propose a competitive release hypothesis to explain how this recombination event could have occurred and why it is evolutionarily advantageous. The findings provide important insights into the natural history of ACE2 usage for both SARS-CoV-1 and SARS-CoV-2 and a greater understanding of the evolutionary mechanisms that shape zoonotic potential of coronaviruses. This study also underscores the need for increased surveillance for sarbecoviruses in southwestern China, where most ACE2-using viruses have been found to date, as well as other regions such as Africa, where these viruses have only recently been discovered.

The evolutionary history of ACE2 usage within the coronavirus subgenus Sarbecovirus.

SARS-CoV-1 and SARS-CoV-2 are not phylogenetically closely related; however, both use the ACE2 receptor in humans for cell entry. This is not a universal sarbecovirus trait; for example, many known sarbecoviruses related to SARS-CoV-1 have two deletions in the receptor binding domain of the spike protein that render them incapable of using human ACE2. Here, we report three sequences of a novel sarbecovirus from Rwanda and Uganda which are phylogenetically intermediate to SARS-CoV-1 and SARS-CoV-2 and demonstrate via in vitro studies that they are also unable to utilize human ACE2. Furthermore, we show that the observed pattern of ACE2 usage among sarbecoviruses is best explained by recombination not of SARS-CoV-2, but of SARS-CoV-1 and its relatives. We show that the lineage that includes SARS-CoV-2 is most likely the ancestral ACE2-using lineage, and that recombination with at least one virus from this group conferred ACE2 usage to the lineage including SARS-CoV-1 at some time in the past. We argue that alternative scenarios such as convergent evolution are much less parsimonious; we show that biogeography and patterns of host tropism support the plausibility of a recombination scenario; and we propose a competitive release hypothesis to explain how this recombination event could have occurred and why it is evolutionarily advantageous. The findings provide important insights into the natural history of ACE2 usage for both SARS-CoV-1 and SARS-CoV-2, and a greater understanding of the evolutionary mechanisms that shape zoonotic potential of coronaviruses. This study also underscores the need for increased surveillance for sarbecoviruses in southwestern China, where most ACE2-using viruses have been found to date, as well as other regions such as Africa, where these viruses have only recently been discovered.

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.

Further Evidence for Bats as the Evolutionary Source of Middle East Respiratory Syndrome Coronavirus.

The evolutionary origins of Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV) are unknown. Current evidence suggests that insectivorous bats are likely to be the original source, as several 2c CoVs have been described from various species in the family Vespertilionidae Here, we describe a MERS-like CoV identified from a Pipistrellus cf. hesperidus bat sampled in Uganda (strain PREDICT/PDF-2180), further supporting the hypothesis that bats are the evolutionary source of MERS-CoV. Phylogenetic analysis showed that PREDICT/PDF-2180 is closely related to MERS-CoV across much of its genome, consistent with a common ancestry; however, the spike protein was highly divergent (46% amino acid identity), suggesting that the two viruses may have different receptor binding properties. Indeed, several amino acid substitutions were identified in key binding residues that were predicted to block PREDICT/PDF-2180 from attaching to the MERS-CoV DPP4 receptor. To experimentally test this hypothesis, an infectious MERS-CoV clone expressing the PREDICT/PDF-2180 spike protein was generated. Recombinant viruses derived from the clone were replication competent but unable to spread and establish new infections in Vero cells or primary human airway epithelial cells. Our findings suggest that PREDICT/PDF-2180 is unlikely to pose a zoonotic threat. Recombination in the S1 subunit of the spike gene was identified as the primary mechanism driving variation in the spike phenotype and was likely one of the critical steps in the evolution and emergence of MERS-CoV in humans.IMPORTANCE Global surveillance efforts for undiscovered viruses are an important component of pandemic prevention initiatives. These surveys can be useful for finding novel viruses and for gaining insights into the ecological and evolutionary factors driving viral diversity; however, finding a viral sequence is not sufficient to determine whether it can infect people (i.e., poses a zoonotic threat). Here, we investigated the specific zoonotic risk of a MERS-like coronavirus (PREDICT/PDF-2180) identified in a bat from Uganda and showed that, despite being closely related to MERS-CoV, it is unlikely to pose a threat to humans. We suggest that this approach constitutes an appropriate strategy for beginning to determine the zoonotic potential of wildlife viruses. By showing that PREDICT/PDF-2180 does not infect cells that express the functional receptor for MERS-CoV, we further show that recombination was likely to be the critical step that allowed MERS to emerge in humans.

Cryptosporidium and Giardia in marine-foraging river otters (Lontra canadensis) from the Puget Sound Georgia Basin ecosystem.

Species of Cryptosporidium and Giardia can infect humans and wildlife and have the potential to be transmitted between these 2 groups; yet, very little is known about these protozoans in marine wildlife. Feces of river otters (Lontra canadensis), a common marine wildlife species in the Puget Sound Georgia Basin, were examined for species of Cryptosporidium and Giardia to determine their role in the epidemiology of these pathogens. Using ZnSO4 flotation and immunomagnetic separation, followed by direct immunofluorescent antibody detection (IMS/DFA), we identified Cryptosporidium sp. oocysts in 9 fecal samples from 6 locations and Giardia sp. cysts in 11 fecal samples from 7 locations. The putative risk factors of proximate human population and degree of anthropogenic shoreline modification were not associated with the detection of Cryptosporidium or Giardia spp. in river otter feces. Amplification of DNA from the IMS/DFA slide scrapings was successful for 1 sample containing > 500 Cryptosporidium sp. oocysts. Sequences from the Cryptosporidium 18S rRNA and the COWP loci were most similar to the ferret Cryptosporidium sp. genotype. River otters could serve as reservoirs for Cryptosporidium and Giardia species in marine ecosystems. More work is needed to better understand the zoonotic potential of the genotypes they carry as well as their implications for river otter health.

Epidermoptid mange in Laysan albatross fledglings in Hawaii.

Mange caused by the epidermoptid mite Myialges nudus (Acari: Epidermoptidae) is described in 31 dead fledgling Laysan albatrosses (Phoebastria immutabilis) from Midway Atoll (Hawaii, USA) sampled from 18 June to 10 July 1990 and from 21 June to 22 July 1991. This is the first record for this parasite from this host. Mites were collected from the skin; were located primarily in the stratum corneum; and were associated with mild to severe granulomatous inflammation, hyperkeratosis, dermal edema, ballooning degeneration of keratinocytes, neovascularization, and subdermal fibrosis. The severity of inflammation in some birds suggested that dermatitis due to M. nudus could be a significant cause of morbidity, or even mortality, in these birds.

T-cell lymphoproliferative disorder in an aged rhesus macaque.

A CD8+ T-cell leukemia was diagnosed in an aged female rhesus macaque. Although leukemia and lymphoma in nonhuman primates are commonly associated with simian T-lymphotropic virus, gibbon ape leukemia virus, oncogenic herpesviruses, and types C, D, and E retroviruses, this monkey was not infected with any of these viruses. However, the monkey did have antibodies against herpesvirus saimiri. This likely represents cross-reactivity of the herpesvirus saimiri assay with rhesus monkey rhadinovirus (RRV) antibodies; RRV was first described in rhesus macaques that were identified as having antibodies against herpesvirus saimiri. Rhesus rhadinovirus is a gamma herpesvirus, related antigenically to herpesvirus saimiri and Kaposi's sarcoma-associated herpesvirus (KSHV), which have been linked to lymphoproliferative disorders in primates and humans, respectively. Moreover, an oncogene has been recently identified in the RRV genome that is equivalent in position to the herpesvirus saimiri and KSHV oncogenes. Presently, the association of RRV infection with disease in nonhuman primates is unknown.

Characterization of the onset of menopause in the rhesus macaque.

The objective of this study was to assess ovarian activity in a cohort of aged female rhesus macaques. Menstrual records for 26 rhesus macaques ages 20-29 yr were evaluated over a 1-yr period, and daily urinary estrone conjugate (E1C) and pregnanediol-3-glucuronide (Hygeia [Hy]-PdG) levels were determined for 12 wk. Each animal was categorized as either pre-, peri-, or postmenopausal based on menstrual and hormonal data. Eleven animals (mean age 22.5 yr) were premenopausal, thirteen (mean age 24 yr) were perimenopausal, and two (mean age 29.5 yr) were postmenopausal. Hormone profiles for perimenopausal animals reveal prolonged follicular phases and/or a lack of patterned Hy-PdG dynamics. Breakthrough bleeding occurred in four of these perimenopausal animals. The postmenopausal animals were amenorrheic and exhibited low E1C levels (less than 10 ng/mg creatinine). The results of this study illustrate that the decline of ovarian function in female macaques during the third decade of life parallels the menstrual and hormonal events associated with the climacteric in women, and that menopause does occur in rhesus macaques.

Reproductive senescence predicts cognitive decline in aged female monkeys.

The present investigation provide evidences from a non-human primate model that naturally occurring menopause predicts a prominent signature of age-related cognitive decline. Young and aged rhesus monkeys were tested on a delayed response (DR) task known to the sensitive to aging, and reproductive status was evaluated according to menstrual cyclicity and urinary hormone profiles. Peri-/postmenopausal monkeys exhibited significant DR impairments relative to either age-matched premenopausal females, or young control subjects. In addition, markers of endocrine decline in the aged animals were selectively correlated with behavioral performance measures that distinguished premenopausal and peri-/postmenopausal monkeys. These results document that menopause is coupled to cognitive decline in the monkey, and they establish a valuable primate model for defining the effects of endocrine aging on brain and behavioral function.

A survey for selected viral, chlamydial, and parasitic diseases in wild dusky-headed parakeets (Aratinga weddellii) and tui parakeets (Brotogeris sanctithomae) in Peru.

Thirty-eight free-ranging dusky-headed parakeets (Aratinga weddellii) and 13 tui parakeets (Brotogeris sanctithomae) were caught and released in Parque Nacional del Manu in southeastern Peru from 19 July to 5 August 1993. Blood and fecal samples were collected and sera were evaluated for titers to Pacheco's disease herpesvirus, psittacine polyomavirus, paramyxovirus-1, and Chlamydia psittaci. Fecal samples were examined for evidence of ascarid or coccidial infection by fecal flotation, and blood smears were examined for hemoparasites. Five (50%) of 10 A. weddellii serum samples tested by complement fixation (CF) for psittacine polyomavirus antibodies were positive, and three (19%) of 16 A. weddellii samples tested by virus neutralization (VN) for psittacine polyomavirus antibodies were positive, yielding a total of 8 (38%) of the 21 A. weddellii samples positive for psittacine polyomavirus. Based on CF for herpesvirus, four (11%) of 38 A. weddellii samples had antibodies against herpesvirus. All B. sanctithomae were negative for psittacine polyomavirus and psittacine herpesvirus. Thirty-five of the A. weddellii tested were negative for Chlamydia psittaci by CF, latex agglutination, and elementary body agglutination, and all B. sanctithomae were negative for Chlamydia psittaci by the CF test. Nine A. weddellii and eight B. sanctithomae evaluated for paramyxovirus-1 titers by the hemagglutination inhibition test were negative. All fecal samples were negative for ascarids or coccidia by fecal flotation, and all blood smears were negative for hemoparasites by direct microscopic examination. This is the first known description of psittacine polyomavirus and psittacine herpesvirus in free-ranging parrots. Serologic evidence of Pacheco's disease herpesvirus in wild A. weddellii is interesting in light of the fact that Aratinga spp. are considered to be possible carriers of this virus in captivity.