ZOONOSIS: Eosinophilic Meningitis caused by Angiostrongylus cantonensis - the Rat Lungworm
When one thinks of rats and the zoonotic diseases they potentially carry, in Jamaica thoughts of leptospirosis immediately spring to mind. However, in a presentation given at the recent University of Technology Scientific Conference, Marco-Dean Brown, graduate student in the Department of Life Sciences, University of the West Indies-Mona, indicated that there is another disease concern - eosinophilic meningitis caused by the rat lungworm Angiostrongylus cantonensis.
According to the presentation, research has shown that rats in all 14 parishes of Jamaica carry the nematode parasite with overall prevalence being 22% (Lindo et al, 2002) to 32% (Waugh et al, 2005). There have been about 24 reported cases or eosinophilic meningitis in humans in Jamaica. A. cantonesis is also known to cause the condition in dogs, though not yet diagnosed here.
While the rat is the definitive host of A. cantonensis, its life cycle also involves a number of intermediate and paratenic (incidental) hosts which could increase the risk to humans and dogs. Mature worms in the rat’s lungs produce eggs which hatch into first stage larvae which migrate up the airways to be swallowed and later passed in the faeces. These develop into infective third stage larvae which are picked up by intermediate hosts, which are snails and slugs, or paratenic hosts, which are lizards, land crabs, freshwater shrimp or planarian flatworms.
Snails and slugs may contaminate vegetables with the infective larvae which are then consumed by humans. The larvae then migrate to the central nervous system and disease results.
After a very variable incubation period of 1 – 3 weeks or more, symptoms very similar to those of bacterial meningitis occur including headaches, stiffness of the neck, nausea, vomiting, abnormal sensations in the limbs . On occasion there may be ocular manifestations. Cerebrospinal fluid cytology reveals high numbers of eosinophils – characteristic of a parasitic condition. Recovery takes 2 – 8 weeks, but in rare cases serious permanent neurological damage or even death can occur, especially in children. There is no specific treatment as anthelminthic therapy could potentially exacerbate the condition due to a systemic response to the dying worms. Treatment is supportive and is corticosteroid-based.
Further research is to be carried out into the prevalence in potential intermediate hosts in Jamaica, using molecular techniques to improve detection.
Angiostrongylosis is another good reason for careful rodent control, as well as snail and slug control for vegetable crops. Freshwater shrimp or land crabs should be properly cooked and raw vegetables thoroughly washed prior to consumption.
For more detailed information on Angiostrongylus cantonensis, please click HERE.
Brown, Marco-Dean, Molecular epidemiology of Angiostrongylus cantonensis in Jamaica, University of Technology Scientific Conference, July 2016
The Ministry of Health recently warned of the possibility of the introduction of a new vector-borne disease - the Zika Virus, also called ZikV. It has made its first appearence in the western hemisphere, with cases being diagnosed in humans in Brazil.
Zika, caused by a Flavivirus - the same family that includes Dengue Fever and West Nile viruses - is classified as an Emerging Disease and is another that had its origins in animals - specifically non-human primates. It is transmitted by Aedes sp. mosquitoes and thus has the potential to spread wherever these insects exist.
It is NOT known to infect any of the domestic animal species so pets, livestock, horses and other animals around us should remain unaffected should the disease arrive on our shores.
The outbreak of Viral Haemorrhagic Fever caused by the Ebola Virus in countries in West Africa has become a global concern in recent weeks. It is a zoonotic disease and so is of concern to the veterinary community which needs to be aware of the role animal transmission plays in its epidemiology.
The Ebola Virus, first identified in 1976 in Zaire (now the Democratic Republic of the Congo) in Central Africa, belongs to the family Filoviridae which also includes the Marburg Virus – the cause of another form of haemorrhagic fever first described in Europe in the 1960’s. Ebola infection in humans results in a severely debilitating illness which has a case fatality rate of 60-90%.
The natural reservoir of the virus is the fruit bat (multiple species) from which infection may from time to time “spill over” into non-human primates (various species of apes and monkeys). The animal-human interface occurs when these animals are handled or consumed by humans – the bats in a soup, and the primates as “bush meat- allowing further “spill over” to the human population after which human to human transmission occurs.
Previous Ebola outbreaks have been usually confined to small communities in which the high mortality rate combined with strict control measures have prevented spread to wider areas. The current outbreak has spread to large population centers where control measures have been hampered by what appears to be a lack of understanding by the public, with some infected individuals avoiding proper medical care and quarantine, thereby spreading the virus more widely. Certain cultural practices have also facilitated spread.
Ebola victims become contagious when they become clinically ill and this continues even after death. Transmission occurs by direct contact with an infected individual, or their body fluids, or indirectly through contaminated materials. Aerosol transmission is NOT an established mode of transmission. Because the early clinical signs and symptoms are shared with so many other diseases, health care personnel or any care-givers are at high risk. Those involved in the burial process of the deceased are also at high risk.
The clinical course of the disease begins following an incubation period of 2 to 21 days (average 8 to 10). Initial symptoms are fatigue, severe headache, fever, myalgia and anorexia which progress to nausea and vomiting, diarrhea, dysphagia, chest and abdominal pain, a skin rash, petechiation, overt haemorrhage (internal, via body orifices), hiccups, somnolence, coma and ultimately death. The blood profile includes leukopenia, thrombocytopenia and elevated liver enzymes.
The Ebola virus. Photo Frederick MurphyDPA - Click the photo for a detailed WHO/PAHO document on Ebola.
Treatment is virtually entirely supportive. The experimental treatment known as ZMapp2 has been used in some patients in the current outbreak with variable success thus far. It is a monoclonal antibody preparation and so attempts to introduce a form of passive immunity to prevent or reduce virus activity until the victim’s own immune system can recover and eliminate the virus. Males that survive the disease may shed virus in their semen for several weeks.
The Caribbean is considered a low risk area for the introduction of Ebola, but nevertheless, given the extent of international travel, the heath authorities must exercise vigilance in the education and monitoring of travelers, as well as establishing protocols to handle any introduced cases, based on international guidelines.
EBOLA VIRUS IN DOGS
A study, conducted in Gabon in during an outbreak in 2001-2002, found that dogs exposed to Ebola by eating infected animal carcasses or licking up body fluids from infected people became infected and seroconverted yet remained asymptomatic. The conclusion drawn from the research is that dogs could potentially be a risk factor for humans during outbreaks, although there is no direct evidence of dog to human transmission. Dogs could also be monitored as a sentinel species.3 Click here for a detailed article.
For a detailed look at Ebola Virus Disease, its epidemiology, clinical course, treatment and control measures please click on the photograph above for a WHO/PAHO/CARPHA presentation1.
1 - WHO/PAHO/CARPHA – Virtual Session for National Authorities in the Caribbean Sub-region
2 - Zmapp - http://en.wikipedia.org/wiki/ZMapp
3 - Allela et al. - Ebola Virus antibody prevalence in dogs and human risk : http://wwwnc.cdc.gov/eid/article/11/3/pdfs/04-0981.pdf
Ebola and Dogs - Is there any risk to humans?
The recent cases in Spain and the United States involving dogs exposed to persons infected with the Ebola virus has caused much discussion in the veterinary community. In Spain, the dog in question was euthanized sparking much outrage in the animal welfare community. In the case of Dallas, Texas, the dog was isolated and cared for while samples were collected at intervals to investigate whether or not the animal contracted the virus.
The truth is that despite all the information we have so far that is strongly suggestive that dogs play no part in the epidemiology of Ebola in humans, there remains some uncertainty as to whether or not they can actually shed virus if it gets into their system. A study carried out in Gabon in 2001-2002 during an outbreak in humans, published in 2005, determined that dogs do get exposed to the Ebola virus by consuming dead wild animals or the discharges from infected people but they do not become ill. They develop antibodies against the virus which circulate in the blood and prevent its further entry. If they do not become sick, it is highly unlikely (though not impossible) that they shed the virus in their body fluids.
Appoximately 25% of the dogs sampled were positive for antibodies. None of the dogs samped tested positive for the virus itself, whether they had antibodies or not. With no virus being found, none of those dogs could, therefore, pose a health risk to humans. Also, in all the past Ebola outbreaks, from its emergence in 1976 to the present, dogs have not figured in the process of containing and stopping the spread of the disease.
However, given that the stakes are so high with the severe threat to human health posed by the virus, all precautions must be taken with dogs that are exposed to infected humans, particularly if they have been in contact with blood, vomitus or faecal material.
The Texas case gave excellent opportunity to begin the process of investigating whether or not it is possible for dogs to shed the virus between exposure and antibody production (seroconversion). The good news is that "Bentley", the 2-year old King Charles spaniel who was held under quarantine since his owner Nurse Nina Pham came down with Ebola has been reuinited with her follwing her recovery. "Bentley" tested negative for the virus during his period in quarantine despite having been with her when she became ill - i.e. he did not contract the virus at all.
Nevertheless, until more information is available, all in-contact dogs must be humanely managed with due diligence and care. The veterinary authorities and community must be prepared for such an eventuality with this disease or any other involving humans and animals.
PLEASE CLICK HERE for more a more detailed look at Ebola.
For information of Ebola in wildlife in endemic areas of the world, plus a look at our own bat species, please visit the Windsor Research Centre websiteHERE.
Chikungunya Virus - the Animal Connection
Chikungunya virus particles: The virus is an Alphavirus of the family Togaviridae (http://www.topnews.in/health/files/Chikv.jpg)
The Chikungunya virus which has been spreading through the Caribbean is primarily a clinical disease of humans, spread by Aedes aegypti and Aedes albopictus mosquitoes. It is believed to have emerged around 1952 in Tanzania, making the jump from chimpanzees to humans1. Subsequently, transmission became human to human via the mosquito vector. There is some evidence that non-human primates, rodents and some wild birds could potentially harbour the virus3.
Animal owners however can rest easy that their pets, livestock, horses etc. will not be at risk of illness.
Animal models, partcularly involving mice and non-human primates have been used to study the pathogenesis of the disease and in ongoing efforts to develop a vaccine2. There is currently no vaccine available and preventive measures are heavily based on vector control to limit transmission.
For more information on the Chikungunya Virus, please click the links to the left for fact sheets from the Centers for Disease Control (CDC) in the United States.
It appears that a significant number of Jamaicans are curious as to whether or not dogs are coming down with the Chikungunya virus - "affectionately" called ChikV. It is only natural that such curiosity should surface given the unprecendented epidemic in the human population and the fact that mosquitoes bite dogs too, spreading heartworm disease in the process.
The good news is that it has never been documented that dogs become ill from ChikV even if it happens to be passed to them by mosquitoes. This virus appears to be very specific for humans, since it made the "species jump" from non-human primates (apes or monkeys) in the 1950's in Tanzania. It follows that any signs of illness seen in dogs during this human epidemic will be related to a range of other illnesses that affect these animals and completely unrelated to ChikV.
Also, persons who suspect their dogs have ChikV might be tempted to give them acetaminophen (Panadol(R), Cetamol(R), Paracetamol(R), Tylenol(R)) for pain. This is a dangerous practice since, although the drug will act in pain relief, more importantly it causes liver damage when given to dogs and cats. While dogs may tolerate and recover from a single dose, this can be fatal for a cat. Repeated dosing can send a dog into fatal liver failure. Therefore, it should never be given to these animals.
The public is advised to consult a veterinarian about illness in their animals and the use of over-the-counter human medications as "first aid" for them.