Veterinary Science and Microbiology

VSC438 Ecology of Infectious Disease

Viruses

Dr. Jim Collins

Viruses and Vectors: From the Panama Canal, the Nile, and Old Tires

 

Topics

ArboViruses …… Spread by Arthropodia (over 700,000 species)

Arthropod-borne viruses

            Flaviviruses:    Yellow Fever, Dengue Fever, West Nile Virus

            Alphaviruses:  Eastern, Western, and Venezuelan Equine Encephalomyelitis

Historical Aspects

Yellow Fever, Dengue Fever, and West Nile virus:

Natural disease,

    …resevoirs,

…vectors,

    …history,

            and human disease.

Emergence of West Nile Virus: Ecological factors

 U.S. status

       Surveillance                      Issues:

 Vector control                  Chemical spraying in metropolitan areas

Equine Clinical Disease (WNV and WEE (=alphavirus group))

Re-emergence: Dengue

Control measures necessary to decrease disease spread

 

Questions:

1. The horse stabled next to your property has been sick for the past two days and has just been diagnosed with West Nile Virus. What measures should you take to protect 1) your horse; 2) your household from infection?

2. Cities like Philadelphia, New York, and New Orleans suffered from Yellow Fever in the 1800’s. What disease control measures were taken to protect the health of the inhabitants of those cities in the 1800’s? Are disease control measures for Yellow Fever still necessary in the U.S.?

3. Define: Enzootic cycle vs Epizootic cycle; Jungle cycle vs Urban cycle;

4. What is the ecological importance (to the virus) of trans-Ovarial transmission?

5. How does one find out if WNV is circulating and is a potential threat to humans?

 

Case: Explain the spread of VNV to over 20 states; if horses are dying is there a risk to humans?

Equine Cases of West Nile Virus Infection
There were 738 cases of clinical West Nile virus (WNV) infection reported in horses from 130 counties in 20 States Of the 738 reported, 651 cases were verified through diagnostic testing at the National Veterinary Services Laboratories of USDA-APHIS. Of those, 640 were classified as confirmed cases and 11 as probable cases. Of 470 horses for which an outcome has been reported, 156 (33.2 percen (WOW!) died or were euthanized.