Biology 1615

Summary Paper

The article “Brush Mouse Population dynamics And Hantavirus Infection During A Warm, Drought Period In Southern Arizona” written by Amy J. Keuenzi, Michael L. Morrison, Nita K Madhav and James N. Mills studies the behavior of Hanta Virus and the various factors that lead to infection on Brush Mouse population(Peromyscus boylii). The study focuses on the Brush Mouse a commonly related rodent to a well-known carrier of the Hanta Virus the Deer Mouse.

The Hanta Virus is a dangerous pathogen that is carried by rodents and easily able to infect humans through contact. The carrier of the virus spreads the disease through their urine and feces. The virus can become airborne when the rodent dropping has become dried and tiny enough that a wind or disturbance can turn it into aerosol.  The diseases cause pulmonary syndrome, hemorrhagic fever, kidney, lung and even heart failure. The symptoms of the Hanta Virus diseases: headaches, fevers, chills, muscle aches, dry cough, shortness of breath and general ill feeling.  The infection does not spread between human to human contacts and each strand is distinct to a certain rodent species carrier. The virus can survive 1 week indoors, and a few hours if exposed to the sun.

The experiment was setup in Santa Rita Experimental Range (Santa Rita Mountains of Arizona.) The area was chosen due to the number high numbers of human infection in the southwest.  The area is also a known habitat for a known carrier host of the Hanta Virus, the Deer Mouse. The Deer Mouse carries the Sin Nobre Virus strand (SNV), while the Brush Mouse carries the Limestone Canyon Virus strand(LSCV).

The experiment consisted of 148 traps set up in three webs like trapping, with each trap spaced evenly apart from one another.  The group conducted the trapping three consecutive days each month for the next 5 years. The Brush mouse that was captured had their gender, weight, age and sexual reproductive condition (sex maturity) recorded, then they were bled for signs of the virus infection. The control group for the experiment was un-bled Brush mouse.  After all the data was collected the animal would be tagged by the ear and released back into its environment.

At the end of the experiment which span from May 1995 to December 1999, the data collected showed a surprising outcome. The Hanta Virus preferred carrier was an adult male at 88%, female were also infected but much lower numbers , while juveniles didn’t have any infection rate. The possible reason for this the author explain is due to territory behavior among male and aggression for mating.

Between 1997 to fall 1999 the Hanta Virus (LSCV) had disappeared among the Brush mouse, when population density had fallen due to drought. The virus reappeared when cool and wet fall weather spurred an increase in population density. The possible reappearance of the virus might be a sole carrier was able to survive the drought and came in contact with the population again, reintroducing it to the area.

The authors conclude that the 5 year experiment was the hottest on record. The increased in temperature is due to climate change and the result from the experiment isn’t typical weather but that of global warming. The relations between weather and population density is due to the fact that Brush mouse breed all year long. When hot, dry temperature create drought, the result is less breeding and less population for the Hanta virus to spread.

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