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It is hypothesized that xenotransplantation could facilitate the emergence of new human pathogens. Retroviruses might pose the greatest public health risk because of the possibility of undetected transmission within a population. Evidence from naturally occurring retroviral zoonoses and cross-species infections by animal retroviruses provides a basis for reasoned speculation on the risks posed by xenotransplantation.
The use of pigs as a source of cells and organs for transplantation has the potential to reduce the current chronic shortage of organs for the treatment of many end-stage diseases. The risk of transmission of infectious agents across the species barrier (zoonoses) has to be assessed. Many such agents can be eliminated from the pig herd. However, porcine endogenous retroviruses, which are carried within the pig genome, are not easily eliminated. They can infect primary and immortalized human cells in vitro, but to date no evidence for in vivo infection has been found in retrospective studies of humans exposed to viable porcine cells. Small-scale clinical trials using porcine cells for the treatment of Parkinson's and Huntington's disease are currently in progress. The prospective monitoring of these patients in conjunction with further research into the biology of this virus will help address safety issues.
BACKGROUND: The orf virus of sheep and goats is one of several zoonotic parapoxviruses. In the ovine/caprine host it causes contagious ecthyma (contagious pustular dermatitis, scabby mouth), but in humans it normally causes solitary or clustered orf lesions, typically on hands, arms or face. In addition to disease in the animals, the virus can be quite a nuisance as an occupational hazard in farmers and butchers. Clinical diagnosis is often possible, but laboratory diagnosis is sometimes necessary. For virus isolation, primary ovine or bovine cells, not routinely present, are needed. Serological methods exist, but electron microscopy is the most commonly used method. OBJECTIVES: To develop a reliable method for the laboratory diagnosis of orf zoonoses, without virus culture and without access to an electron microscope. STUDY DESIGN: A suitable primer pair was designed for orf polymerase chain reaction (PCR), using the Oligo software and sequence information from GenBank. Orf positive controls and specimens were kindly provided by several public health centers. Molluscum contagiosum specimens were provided by a dermatologist. HSV-1, HSV-2 and VZV positive swab specimens came from our routine diagnostic service. Asymptomatic skin specimens were obtained from sheep heads from the abattoir, and swab specimens from the heads of asymptomatic sheep. Selected amplified orf PCR positive specimens were sequenced to ensure the authenticity of the PCR products. Orf positive specimens were sent to another laboratory for electron microscopy. RESULTS AND CONCLUSIONS: A robust PCR was developed, with very small inter-run variation. All specificity demands were met, and the sensitivity seems to be good or excellent. All negative specificity controls from cell cultures and non-orf viruses were negative. Twenty-two (95.7%) of 23 scab or swab specimens with suspected orf etiology were orf PCR positive. Five of eight skin specimens from sheep heads from the abattoir were positive, and all 11 swab specimens from asymptomatic sheep were negative. Electron microscopy demonstrated orf-like particles in orf-PCR positive specimens. This PCR seems to be suitable as a diagnostic test for orf in humans, but asymptomatic virus shedding in sheep or goats may complicate veterinary applications of the assay.
The importance of foodborne parasitic zoonoses remains high in many regions of the world. Although control efforts have been exerted for quite some time, overall progress has not been satisfactory, even in many well developed countries. An important drawback in control programmes for parasites such as Trichinella, Toxoplasma and Taenia has been the absence of rapid, accurate and sensitive diagnostic tests for these meatborne parasites. However, the rapid advances in the molecular biology of these organisms has yielded concomitant gains in precision of detection. This review highlights these advances and their impact or potential application to the control of foodborne parasites.
The ability of three avian viruses to elicit antibody response in humans was surveyed for the purpose of identifying zoonotic diseases. Antibody levels in people associated with poultry were compared to those in people having limited poultry association. Antibody levels to three avian viruses: infectious bursal disease virus, a birnavirus; Newcastle disease virus, a paramyxovirus; and avian infectious bronchitis virus, a coronavirus were determined by enzyme-linked immunosorbent assays (ELISA). Differences between the two study groups were evident: people having a known association with poultry showed significantly higher levels of antibodies to Newcastle disease and avian infectious bronchitis virus. Antibodies detected may be due to virus exposure rather than zoonoses.
The importance of latent zoonoses has increased in recent years in view of foodborne diseases: (i) the "healthy" animal repesents a reservoir for specific pathogens; () no pathological-anatomical changes in the carcass and its organs show the presence of these pathogens; and (iii) these pathogens may enter the food chain via hygienic weak points in the slaughtering process. To estimate the risks involved and to take appropriate measures, analysis of the slaughtering process should be complemented by collecting data relating to the carriage of the animals of latent zoonotic pathogens. From October 2004 to June 2005, fecal samples from 630 slaughtered sheep were enriched and then examied by IMS technique and by PCR to assess the prevalence of E. coli O157 (OE). Seven samples (1.1%), distributed throughout the whole examination period, were found to be positive. To assess the potential pathogenicity for humans, E. coli O157 strains were isolated by colony hybridization and further characterized. The isolated strains fermented Sorbitol, showed four different H tys (H7, H12, H38, H48), and were all negative for stx. One O157:H7 strain harbored the gene for intimin (eae) in combination with ehxA, and paa. In consequence, the potential health hazard from sheep meat related to O157 STEC seems current not to be of particular importance in Switzerland. Results emphasize the fact that E. coli O157 are not always STEC but may belong to other pathotypes as nontraditional EPEC.
Among transmissible diseases, vectorial diseases represent a major problem for public health. In the group of acarina, while ticks are the most commonly implicated vectors, other arthropods and notably Dermanyssoidea are also involved in the transmission of pathogenic agents. Since the role of this superfamily is at present largely unknown, we have reviewed the vectorial role of these mites in the appearance, survival and propagation of pathogens. Various authors have shown that Dermanyssoidea are implicated in the transmission of both bacteria (Salmonella, Spirocheta, Rickettsia or Pasteurella) and viruses (equine encephalitis viruses, West Nile virus, Fowl pox virus, the virus causing Newcastle disease and tick borne encephalitis viruses or hantaviruses). Finally, some authors have also shown their role in the transmission of some protozoa and filaria. As the vectorial character of such mites has been more clearly demonstrated (Dermanyssus gallinae, Omithonyssus bacoti and Allodermanyssus sanguineus), it would be interesting to continue studies to better understand the role of this superfamily in the epidemiology of certain zoonoses.
Animal-assisted activity/therapy (AAA/T) is an emerging science using animals to solve human problems. It is an interdisciplinary approach using animals as an adjunct to other conventional therapies. The benefits include improved physical, social, emotional or cognitive functioning. Studies in the past have shown lowering of blood pressure and increased survival in those who own a pet. This may not be effective for all individuals, however, it is essential that a complete assessment be made before implementation of AAA/T. The goals of such a therapy must be defined. Animal bites, allergies and zoonoses are the major animal-associated health hazards. The type of AAA/T and needs of the patients are important issues to be considered. Specific guidelines including suitability of patients, animals and infection control policies need to be formulated before initiation of AAA/T. Such an intervention would also require additional resources and there may be legal implications.
Although there are over 250 zoonotic diseases, only 30-40 of them involve dogs and cats. Transmission of zoonotic infections occurs via bites, scratches or touch; exposure to saliva, urine or feces; inhalation of particles or infectious aerosols; contact with a transport or intermediate host (e.g. ticks, fleas); or exposure to contaminated water, soil or vegetation. This paper summarizes the most important common zoonotic dermatological diseases of dogs and cats. The most common dermatological zoonoses are flea and tick infestations and the diseases they transmit; dermatophytosis; and mite infestations (Sarcoptes and Cheyletiella). Prevention of zoonotic infestations or infections can be accomplished easily by the use of routine flea and tick control, screening of new pets for dermatophytosis, and routine hand-washing.
The Monti Sibillini National Park is a recently borne protected area in the central Apennines that has become an important tourist destination. Mountain grasslands and woods have made it also a suitable habitat for sheep and bovine cattle, as well as for wild animals such as the wild bore and the roe deer. Therefore, a preliminary investigation was conducted to assess the risk of transmission of tick-borne zoonoses, such as Lyme disease and Babesiosis, by actively looking for both the arthropod vector and the causative agent. For two consecutive years, ambushing ticks were collected in four distinct geographical areas, comprehensive of many highly frequented tourist places. The tick fauna, tick habitats and the seasonal distribution of the different tick life stages collected with the method of "flagging and dragging" have been reported. Almost all the collected specimens belonged to the species Haemaphysalis punctata (Canestrini and Fanzago) (Acari: Ixodidae), which was found moderately infected with Babesia spp. Only a few Ixodes ricinus (Linnaeus) ticks, the most competent vector of Lyme disease, were found and on PCR examination all of them resulted negative as far as the infectious agent Borrelia burgdorferi sensu lato (Johnson) is concerned.
Lyme disease, first identified in 1975, is the most recently recognized of the seven human spirochetal diseases; the evolving clinical picture of Lyme disease indicates it shares many features with the other diseases. These similarities are striking in view of the diverse epidemiology of the seven diseases, which are caused by Treponema species (spread by human-to-human contact) or Leptospira or Borrelia species (zoonoses). These similarities include the following: (1) skin or mucous membrane as portal of entry; (2) spirochetemia early in the course of disease, with wide dissemination through tissue and body fluid; and (3) one or more subsequent stages of disease, often with intervening latent periods. Lyme disease shares with many spirochetal diseases a tropism for skin and neurologic and cardiovascular manifestations, whereas chronic arthritis is unique to Lyme disease. These similarities and dissimilarities offer opportunities to discover which properties unique to the pathogenic spirochetes are responsible for clinical manifestations and suggest that certain clinical features of patients with spirochetal diseases other than Lyme disease may someday be recognized in patients with Lyme disease.
Departments of public health and agriculture in all 50 states of the United States and the District of Columbia were queried in 1977 to determine which of some selected zoonoses are reportable, the method of reporting and the diagnostic stage at which reporting is required. Fifty-three of the 62 diseases on the public health questionnaire were listed as reportable, with hepatitis A required by 49 of the 51 jurisdictions. Telephone reporting was required in nearly 19% of the disease-jurisdiction combinations and, in nearly 55%, reporting was required when the disease first was suspected. Thirty-three of the 41 diseases on the agriculture questionnaire were reportable, with anthrax most frequent. Telephone reporting was required in 30% of the reportable situations and suspected diagnoses were reportable in 54%. The disease lists varied markedly between the public health and agriculture agencies.
Cross-species transfers of pathogens (zoonoses) cause some of the most virulent diseases, including anthrax, hantavirus and Q fever. Zoonotic infections occur when a pathogen moves from its reservoir host species into a secondary host species. Similarly, commensal infections often have a primary reservoir location within their hosts' bodies from which they rarely cause disease symptoms, but commensals such as Neisseria meningitidis cause severe disease when they cross into a different body compartment from their normal location. Both zoonotic and commensal infections cause either mild symptoms or severe disease, but rarely intermediate symptoms. We develop a mathematical model for studying three factors that affect the probability of severe disease: the size of the inoculum, the route of inoculation and the frequency of naturally occurring infections that do not cause symptoms but do induce protective immunity (vaccinating inoculations). With a single route of infection, increasing pathogen density causes inoculations to develop more often into disease rather than asymptomatic vaccinations that provide protective immunity. With two routes of infection, it may happen that a lower density of a pathogen or of a particular antigenic variant leads to a relatively higher frequency of disease-inducing versus vaccinating inoculations. This reversal occurs when one route of infection tends to vaccinate against relatively common pathogens but less often vaccinates against relatively rare pathogens, whereas the other route of infection is susceptible to disease-inducing inoculation even at relatively low pathogen density.
One hundred and thirty-six women from an urban, rural and farming community were recruited to a study of infectious causes of midtrimester miscarriage (n = 85), stillbirth (n = 32), or termination for developmental (n = 17) or chromosomal (n = 2) abnormalities. No woman had evidence of acute infection with toxoplasma, listeria, leptospira or Chlamydia psittaci (ovine enzootic abortion). One woman had midtrimester miscarriage associated with primary cytomegolovirus infection and five women had evidence of parvovirus B19 infection, although fetal infection was not proven. Zoonoses were not identified as a cause of fetal loss or malformation in this at-risk population, but parvovirus B19 was a significant cause of midtrimester fetal loss.
Based on findings demonstrating the simian ancestry of HIV, AIDS has been reported to be a zoonosis. However, this theory has never been proved and must seriously be questioned. Several arguments show that HIV-AIDS is not a zoonosis. (i) If AIDS were a zoonosis, there must be evidence of AIDS being directly acquired from an animal species, as is rabies, a disease that is directly acquired from animals. (ii) Despite long-term and frequent human exposure to SIV-infected monkeys in Africa, only 11 cross-species transmission events are known, and only four of these have resulted in significant human-to-human transmission, generating HIV-1 groups M and O and HIV-2 groups A and B. The closest relatives of SIVcpz (HIV-1 group N) and of SIVsm (HIV-2 groups C-H) are extremely rare, with only six HIV-1 group N-infected patients and only single individuals known to be infected by HIV-2 groups C-H. SIV, while capable of cross-species transmission, is thus poorly adapted for disease and epidemic spread. If AIDS were a zoonosis that is capable of significant human-to-human spread, there would be a plethora of founder subtypes and groups. (iii) Human exposure to SIV is thousands of years old, but AIDS emerged only in the 20th century. If AIDS were a zoonosis that spread into the human population, it would have spread to the West during slave trade. (iv) Experimental transmission of SIVs to different species of monkeys is often well controlled by the new host, showing that the virus and not the disease is transmitted. Therefore, we conclude that cross-species transmission of SIV does not in itself constitute the basis for a zoonosis. Transmission per se is not the major requirement for the generation of the AIDS epidemic. All HIVs do derive from simian species, but AIDS does not qualify as a zoonosis and this explanation cannot in itself account for the origin of AIDS epidemic. It is important to distinguish AIDS from true zoonoses (e.g. rabies) because research is needed to understand the processes by which animal viruses cause sustained human-to-human transmission, epidemics and even pandemics. Much is known about emerging viruses, but almost nothing is known about emerging viral diseases.
Foot-and-mouth disease (FMD) was introduced into the Americas in 1870. At that time the disease was described simultaneously in the North coast of the United States of North America, the Province of Buenos Aires in Argentina, the central region of Chile, Uruguay, and South Brazil. At the beginning of the twentieth century the disease spread to the rest of Brazil, Bolivia, Paraguay, and Perú. In 1950 the disease was introduced into Venezuela, and in the same year to Colombia, and from there to Ecuador. The United States of America eradicated an outbreak of FMD in 1929. Outbreaks of FMD were also eradicated from Mexico in 1947 and from Canada in 1952. The last outbreak that occurred in Mexico in 1954 was also eradicated. In 1951 the Americas Animal Health Authorities decided to establish a Pan-American Foot-and-Mouth Disease Center (PANAFTOSA), initially as a special program within the American States Organization (OAS). The center was later transferred to the Pan-American Health Organization (PAHO). In the early 1970s PANAFTOSA developed a proposal for a continental surveillance system for vesicular diseases, which was approved by Agriculture Ministers at an International Meeting for FMD and Zoonoses (RICAZ). Since then, PANAFTOSA dedicated all efforts to collaborate with each country in the implementation of the system and to receive, analyze, and distribute a weekly report of vesicular diseases. The model was elaborated using coordinate grid maps, one for the South American Continent, others for each country in the region. The reports from each country consist of the grid location for any suspicious outbreak of vesicular disease. Using the information gathered during visits to the countries, as well as weekly reports, and by studying the most frequent animal movements within the region, PANAFTOSA developed a proposal for FMD eradication. This plan was approved by the Government of South America and implemented in cooperation with PANAFTOSA. The hemispheric plan for FMD eradication (PHEFA), has been implemented and today Chile and Uruguay are FMD free without vaccination; Argentina, Paraguay, and the states of Rio Grande do Sul and Santa Catarina in Brazil are also recognized by the OIE to be FMD Free, with vaccination. The use of the continental surveillance system is the main strategy for achieving the eradication of FMD in South America. At this time PANAFTOSA is working to improve the system, and to add other diseases indicated by the governments of the Americas.
Vibriosis is an economically important disease of fish, marine invertebrates (particularly penaeid shrimps), and large marine mammals and is responsible for high mortality rates in aquaculture worldwide. Some Vibrio species are also responsible for zoonoses, whereas others are relatively nonpathogenic. Using 16S- and 23S-based PCR reactions, we obtained species-specific patterns and a 470-bp band, respectively. DNA sequences obtained on the 23S rRNA gene allowed us to identify species-specific probes for Vibrio parahaemolyticus, V. alginolyticus, V. anguillarum and for a cluster of taxonomically related species: V. carchariae/harveyi/campbelii. A phylogenetic tree based on the 23S sequences confirmed previous results obtained by Western blotting.
Outbreaks of anthrax zoonose occurred in two regions of France in 1997. Ninety-four animals died, and there were three nonfatal cases in humans. The diagnosis of anthrax was rapidly confirmed by bacteriological and molecular biological methods. The strains of Bacillus anthracis in animal and soil samples were identified by a multiplex PCR assay. They all belonged to the variable-number tandem repeat (VNTR) group (VNTR)3. A penicillin-resistant strain was detected. Nonvirulent bacilli related to B. anthracis, of all VNTR types, were also found in the soil.