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.

Zoonotic protozoa in the marine environment: a threat to aquatic mammals and public health

This collection of abstracts provides an account of four presentations at the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP)(held in New Orleans, LA, USA from 10–14 August 2003) in a symposium session on zoonotic protozoan parasites found in the marine environment and chaired by Ronald Fayer and David Lindsay.The focus was on three genera of parasites of veterinary and public health concern—Toxoplasma,Giardia, and Cryptosporidium with emphasis on their epidemiology in the marine environment.

[Hypocomplementemic vasculitis treated with dapsone]

BACKGROUND

Hypocomplementemic urticarial vasculitis, described by MacDuffie in 1973, is rare. Some doubt surrounds its classification. We report a case of hypocomplementemic urticarial vasculitis (MacDuffie syndrome) treated with dapsone with a favorable outcome.

CASE REPORT

Over a number of years, a 43-year-old man presented urticarial vasculitis attacks with palpebral oedema and systemic symptoms such as fever and arthralgia. In 2006, MacDuffie syndrome was diagnosed on the grounds of positive anti-C1q antibodies. Treatment with dapsone was started and resulted in considerable improvement.

DISCUSSION

Hypocomplementemic urticarial vasculitis is characterized by urticarial vasculitis lesions, leucocytoclastic vasculitis and systemic symptoms. The latter symptoms are similar to those of systemic lupus erythematosus (SLE), and some authors have suggested that MacDuffie syndrome may in fact belong to SLE. Diagnosis is based on clinical appearance, histology and the presence of anti-C1q antibodies. There is no specific treatment for hypocomplementemic urticarial vasculitis. Immunosuppressant therapy can be used for lesions refractory to systemic corticosteroids.

[BCG infection of the glans penis after intravesical BCG therapy]

BACKGROUND

BCG therapy is an effective adjuvant treatment for superficial bladder tumors. Therapy involves intravesical instillation of live attenuated Calmette-Guérin bacilli. BCG infection of the glans is a rare local complication associated with this treatment, two cases of which are reported below.

PATIENTS AND METHODS

Case 1: A 77-year-old man presented relapsing urothelial bladder carcinoma treated by endoscopic resection and BCG therapy. One week after the seventh instillation, severe balanitis developed. Three months later, examination revealed massive painful perimeatal ulceration with yellowish papules in the peripheral regions. Histology revealed epithelioid giant-cell granulomas. Ziehl-Neelsen staining was positive. Slow cure of the lesions was achieved within 12months using double antitubercular antibiotic therapy. Case 2: In a 61-year-old man receiving BCG therapy for relapsing bladder carcinoma in situ, the sixth instillation was considered traumatic since it was highly painful. One week later, papular nodules appeared on the glans with a sclerosing lesion of the balanopreputial sac, dark purple perimeatal papules and a mass beneath the mucosa of the glans. Antibiotic treatment comprising ofloxacin followed by rifampicin for two months proved ineffective. Histology revealed granulomatous dermal lesions with eosinophilic necrosis. Triple antitubercular antibiotic therapy was initiated.

DISCUSSION

The first reported case of BCG infection of the glans in patients undergoing intravesical BCG therapy was published in 1992. Since then, there have been nine other reports. There is no stereotypical clinical presentation. In most cases, an infiltrated erythematosus plaque is seen together with yellowish papules in certain patients. Diagnosis is based upon history and histological examination.

Vaccination in conservation medicine

Unprecedented human population growth and anthropogenic environmental changes have resulted in increased numbers of people living in closer contact with more animals (wild, domestic, and peridomestic) than at any other time in history. Intimate linkage of human and animal health is not a new phenomenon. However, the global scope of contemporary zoonoses has no historical precedent. Indeed, most human infectious diseases classed as emerging are zoonotic, and many of these have spilled over from natural wildlife reservoirs into humans either directly or via domestic or peridomestic animals. Conservation medicine has recently emerged as a meaningful discipline to address the intersection of animal, human, and ecosystem health. Interest in the development of novel vaccines for wildlife encounters important challenges that may prevent progress beyond the conceptual phase. Although notable examples of successful wildlife immunisation programmes exist, depending upon key considerations, vaccination may or may not prove to be effective in the field. When implemented, wildlife vaccination requires a combination of novel zoonosis pathogen management strategies and public education to balance conservation, economic, and public health issues.

Transmission of Toxoplasma: clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment

Toxoplasma gondii affects a wide variety of hosts including threatened southern sea otters (Enhydra lutris nereis) which serve as sentinels for the detection of the parasite's transmission into marine ecosystems. Toxoplasmosis is a major cause of mortality and contributor to the slow rate of population recovery for southern sea otters in California. An updated seroprevalence analysis showed that 52% of 305 freshly dead, beachcast sea otters and 38% of 257 live sea otters sampled along the California coast from 1998 to 2004 were infected with T. gondii. Areas with high T. gondii exposure were predominantly sandy bays near urban centres with freshwater runoff. Genotypic characterisation of 15 new T. gondii isolates obtained from otters in 2004 identified only X alleles at B1 and SAG1. A total of 38/50 or 72% of all otter isolates so far examined have been infected with a Type X strain. Type X isolates were also obtained from a Pacific harbor seal (Phoca vitulina) and California sea lion (Zalophus californianus). Molecular analysis using the C8 RAPD marker showed that the X isolates were more genetically heterogeneous than archetypal Type I, II and III genotypes of T. gondii. The origin and transmission of the Type X T. gondii genotype are not yet clear. Sea otters do not prey on known intermediate hosts for T. gondii and vertical transmission appears to play a minor role in maintaining infection in the populations. Therefore, the most likely source of infection is by infectious, environmentally resistant oocysts that are shed in the feces of felids and transported via freshwater runoff into the marine ecosystem. As nearshore predators, otters serve as sentinels of protozoal pathogen flow into the marine environment since they share the same environment and consume some of the same foods as humans. Investigation into the processes promoting T. gondii infections in sea otters will provide a better understanding of terrestrial parasite flow and the emergence of disease at the interface between wildlife, domestic animals and humans.

Implementation and evaluation of a strategic parasite control program for captive exotic ungulates

A parasite control program was designed for greater than 1,200 exotic ungulates maintained in mixed-species enclosures at the San Diego Wild Animal Park. Three strategically-timed anthelmintic treatments were given during 1988-1989, and their success was evaluated by monitoring pretreatment and posttreatment fecal egg counts. Adequate parasite control was achieved for animals in 52 ungulate species, as evidenced by low pretreatment egg counts and the absence of egg-shedding after treatment. However, animals belonging to 11 species in the subfamilies Antilopinae, Hippotraginae, and Caprinae were identified as important targets for more intensive control efforts because they shed either greater than 100 eggs/g of feces before treatment, or greater than 0 eggs/g after treatment, at 2 or more sampling periods. These results and observations were used to generate management recommendations and illustrate how a model parasite control program can be developed for collections of exotic ungulates.