Category Archives: Kill the wabbit!
Gracen Schilling (12:00 Micro) found an article from Science Daily describing research from the University of Illinois on retroviruses from an unusual mammalian research system. Here is Gracen’s summary:
Scientists from the University of Illinois have found that koalas have a retrovirus that infects them, similar to the ones found in human genomes. Since 8% of our genomes derive from retroviruses, this new knowledge will give us the ability to understand our own viral lineage. The koala retrovirus (KoRV) was found in 39 different forms, all which are endogenous. Endogenous retroviruses are ones that are passed down from the one parent, or the other, to the baby. One endogenous KoRV was even found in both parents. The fact that koalas are the only other animal to transition from exogenous to an endogenous retrovirus gives us a way to understand how our own retrovirus evolved. Exogenous retroviruses are ones that infect a host, insert into to host cells genetic information, and then uses its hosts to create more viruses alike. The way a retrovirus becomes endogenous is when the exogenous retrovirus infects an egg or sperm cell, causing the viral genetic information to be passed to an offspring. Unlike humans however, the KoRV is in its beginning stages of development in koalas. However, this means we will be able to learn how to help the koalas deal with the retrovirus until it is no longer harmful. Over the thousands of years since the virus integrated with the koalas, it has been noted that they have suffered different physical effects. Just like us humans, the koalas will likely survive and adapt to the genetic changes going on despite the fact it is a long, slow and painful process. Once the retrovirus becomes part of the host, however, it will become more helpful than harmful, because the retrovirus will begin to help the host since it is the best way to ensure its own survival.
It is important to know that the likelihood of the thousands of KoRV’s in the koalas surviving is slim to none. Even though they found tens of thousands in the koalas, one hundred may survive. Most will disappear because some of the viruses are only present in one chromosome, so if it does not reproduce or is passed down than it disappears. The ones that are passed down are protected by the DNA repair mechanisms of the koala, so the reproduction of the viruses is very slow. Researchers estimated that the KoRVs were integrated into koalas less than 50,000 years ago. While this may seem like a long amount of time, it really is not considering some are millions of years old. Overall, this discovery is huge for us since it will show us not only how to help koalas to survive the retrovirus process, but by also allowing us to see how our retrovirus history originated.
The latest issue of the CDC’s Morbidity Mortality Weekly Report has brought to my attention an update on Hansen’s Disease (aka Leprosy) in the United States for the past 15 years. Leprosy is a sporadic disease in the US, with an annual incidence rate of about 1 case per million people. The incidence outside of the US is higher. It is caused by the acid-fast bacterium Mycobacterium leprae, and according to this recent review article, seems to be transmitted via nasal secretions although only poorly. The incubation period for the development of disease is long; generally about 3 to 7 years, and initially presents with numbness in the peripheral nerves and flat skin lesions. Because of the very long incubation period, diagnosis is frequently delayed and at that point the treatment options become limited.
The World Health Organization is leading a global effort to eliminate Hansen’s Disease, and is beginning to show some marked success. To facilitate this effort, epidemiologists from the CDC examined reported data for the period from 1994 to 2011. They found that overall the rate of leprosy has declined during that time period, however the rate among people not born (but diagnosed in) the US was about 10 times higher than the rate for people born in the US. Clinicians noted that many of the cases were in patients from nations in the Southern Pacific (Oceania); indeed Hansen’s Disease is one that immigrants are screened for when they enter the US, however if they do not apply for Permanent Residency, they forego that screening. The CDC recommends that to effectively eliminate Hansen’s Disease clinicians here need to be further educated about the disease and its symptoms among high risk populations in order to monitor recent immigrants. Resources also should be expanded to enable clinicians outside the US to diagnose the disease earlier. The CDC notes that an early diagnosis of Hansen’s Disease is critical to prevent further transmission, and to prevent lifelong disability from the disease.
A viral outbreak of a canine circovirus has struck some of our four legged friends in California, Ohio, and Michigan. The canine circovirus has caused several deaths in September, October and November of the present year. The American Veterinary Medical Association first identified the canine version of the circovirus in June 2012. Prior to June of 2012, the American Veterinary Medical Association (AVMA) only recognized the circovirus infecting those of the avian and pig populations. The first case of canine circovirus was reported in a California dog at the UC Davis School of Veterinary Medicine. Although the AVMA has claimed the actual means of transmission have not been identified yet, they believe healthy dogs contract the virus through direct contact with the salvia, feces, or vomit of an infected dog. The major symptoms of canine circovirus infection include diarrhea, extreme lethargy, bloody stools, and vomiting. The AVMA also ensures dog owners not to worry over the likelihood of mortality due to infection. Early treatment of diarrhea and vomiting will greatly improve rate of survival in the infected dog. Therefore, if dog owners suspect their dogs are suffering from a canine circovirus infection, the AVMA advise immediate diagnosis and treatment from a veterinary clinic or emergency animal hospital.
Interestingly enough, not every single dog that comes into contact with the canine circovirus will become infected. In fact, researchers at the UC Davis School of Veterinary Medicine found that out of two hundred and four healthy adult dogs, fourteen of the dogs showed traces of the canine circovirus in fecal samples. However, the fourteen dogs did not show signs or symptoms of infection. Therefore, some dogs can be carriers for the virus. The carriers unknowingly transfer the canine circovirus to other healthy dogs through communicable direct contact. Researchers from the UC Davis School of Veterinary Medicine are unsure whether the canine circovirus independently causes infection and illness or if the canine circovirus works with another etiologic agent. Since the circovirus has only recently been discovered in the canine population, scientists must undergo more research to have a better understand of the circovirus’ pathogenesis.
In the realm of morphology and other microbiology classifications, the canine circovirus, sometimes mentioned as Dog CV in scientific journals, is non-envelopled and spherical in shape. The canine circovirus consists of a single stranded circular DNA genome. The canine circovirus is a member of the Circoviridae family and the Cuclovirus and Gyrovirus genus. Recently, the American Society for Microbiology published an article, Complete Genome Sequence of the First Canine Circovirus, in their subdivision Journal of Virology. Virologists Amit Kapoor, Edward Dubovi, Jose Henriquez-Rivera, and W. Lipkin assisted in the first genome sequence of the canine circovirus, CaCV-1 strain NY214. In the single stranded circular DNA, approximately 2,063 nucleotides were sequenced. By sequencing the DNA genome, virologists believe that they are one step closer to understand the evolutionary and pathogenic characteristics of the mammalian circoviruses. One day, virologists hope to understand the mutation that allows circovirsues to jump from one host, like the pig or bird, to another host, like the dog.
Now, dog owners of America, don’t fret! Remember to keep your loyal companion away from dog parks, dog kennels, and other places where your buddy could come into contact with other dogs since these canine crowded areas tend to become susceptible reservoirs. Since the canine circovirus is transmitted directly, do not allow your dog to come into contact (eat) other dog’s saliva, feces, or vomit. If your dog exhibits any possible signs of infection, like extreme lethargy, vomiting, or bloody stools, please contact a veterinarian or emergency animal hospital immediately.
I fully expected to see an alert like this via the “Notes from the field” briefs from the Centers for Disease Control and Prevention, however it was CBS Channel 4 in Minneapolis that broke this story. Earlier in August, 81 people were sickened with salmonellosis at an Ecuadoran Independence Day festival in Minneapolis. Public health officials have said that people were reporting severe gastroenteritis symptoms, and many of them tested positive for Salmonella in lab tests. All patients reported eating guinea pig meat served by one of the festival’s vendors.
The list of animal reservoirs that can carry Salmonella is impressively long; indeed guinea pigs are one animal that is explicitly listed by the CDC on their Salmonella page. A research article from 1966 indicated that it has historically been a sufficiently significant problem that there was initiative to create a Salmonella–free breeding colony for research purposes, and the “only registered small animal hospital” in South East Ireland indicates that salmonellosis is one of the most significant zoonotic infections from guinea pigs. Since the animals are frequently in the carrier state, the pathogen is unlikely ever to be eliminated.
However, the only previous outbreak directly attributable to guinea pigs that I’ve been able to find was published at the 2012 International Conference on Emerging Infectious Diseases (abstract 286: “Outbreak of Salmonella enterica serotype Enteritidis Infections Associated with Pet Guinea Pigs— Multiple States, 2010”). In that outbreak, 10 patients across 8 states developed Salmonella infections with guinea pig association. Molecular analysis indicated that the patient isolates were related, however no clear chain connecting animal distributors to pet shops could be identified. The report ended with the recommendation that consumers and the pet industry should be educated about the risks due to infection from “pocket pets”. The best protections continue to be two-fold; first, always make sure to wash your hands following handling of animals, and second, make sure that you cook them to an internal temperature of at least 165 degrees Fahrenheit.
You may recall that there is some controversy as to the extent and nature of the Rabbit Menace. Here is another data point for you to consider, before you head off to PetSmart to get your new companion. Via the journal Global Change Biology, a tale to terrify you.
Many herbivores carry a variety of intestinal helminth parasites, which are acquired during feeding and passed on in the feces. Two soil dwelling helminth parasites of the European rabbit (Oryctolagus cuniculus) have been used to model the interactions between hosts and pathogens in controlled laboratory systems. The nematodes Graphidium strigosum and Trichostrongylus retortaeformis have been extensively studied in the rabbit for decades. Neither nematode typically causes a lethal infection in rabbits, but does lead to weight loss and decrease in fecundity in infected animals. A quick search through Pubmed did not turn up any obvious infections of humans, but presumably the elderly, the very young, and otherwise immunocompromised are at some measure of risk of infection.
The current study focuses on the ambient temperature, egg hatching rates of the nematode in soil, and survival of the larvae, and came about due to observations of generally increasing air temperature measurements at the study site over a 30 year period. These observations have led the authors to question whether host/parasite dynamics might additionally be affected by environmental conditions. What they found was that T. retortaeformis, but not G. strigosum, showed higher rates of egg hatching and larval survival with increases in temperature. This result contrasted the 30 year period of field studies, which indicated that G. strigosum infection rates increased during the interval of generally increasing ambient temperature trends.
Overall, the study underscores the dynamic nature of the host/parasite interaction, and the potential that shifting environmental conditions enable certain microorganisms to have competitive advantages over others. Although both of these worm pathogens pose no known risk to humans, many other bacterial, fungal, protozoan, and metazoan pathogens of humans may demonstrate similar responses to altered environmental conditions seen, as mean global temperatures continue to increase.
As part of my weekly review of the current threats to the health of BIO230 students, I located this article from the Centers for Disease Control and Prevention detailing a multistate outbreak of Salmonella attributable to pet hedgehogs. As of early September, a total of 14 individuals across 6 states have come down with illness. Three individuals required hospitalization, however none of the illness resulted in death. Analysis of the etiologic agent in the outbreak has indicated that the hedgehogs were purchased from multiple breeders in the various states, suggesting that this is not a sole-source outbreak like my last animal-Salmonella outbreak detailed here.
As part of their standard warnings to consumers, the CDC reiterates:
- wash your hands after handling hedgehogs or “anything where they live or roam”
- do not snuggle or kiss hedgehogs
- do nob bathe hedgehogs in the kitchen sink or in the bathroom
- be careful with children and hedgehogs
Some terminology clarification might be useful at this point. Although the Salmonella outbreak in this case is due to the presence of an animal reservoir and Salmonella species are part of the intestinal flora of animals, I don’t think I would strictly term this outbreak as a zoonosis, because the disease salmonellosis may be acquired from a number of different sources including from infected humans. It would really be much better defined as an environmentally acquired disease. However, since no concrete link exists at this point between the infected hedgehogs, it may be safe to assume that hedgehogs can carry Salmonella as part of their normal microbial flora, and that the outbreak was not due to hedgehogs becoming carriers due to a single infection source.