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Lofgren's disease has been observed frequently in commercially raised cattle but very rarely in chickens. Both cattle and chickens raised for meat are often fed the type of feed that transmits the virus that causes the disease. Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease, however, and chickens commercially raised for meat, unlike cattle, are generally brought to market during their first year of life.
Which of the following is most strongly supported by the information provided?
| Passage Statement | Visualization and Linkage |
|---|---|
| Lofgren's disease has been observed frequently in commercially raised cattle but very rarely in chickens. | Disease Prevalence Pattern:
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| Both cattle and chickens raised for meat are often fed the type of feed that transmits the virus that causes the disease. | Exposure Factor:
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| Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease, however, and chickens commercially raised for meat, unlike cattle, are generally brought to market during their first year of life. | Timing Mismatch:
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| Overall Implication | The timing paradox explains the frequency difference: chickens likely contract the virus at similar rates to cattle but are brought to market before the disease becomes observable, creating the illusion of lower infection rates. |
Inference: The low observed frequency of Lofgren's disease in chickens compared to cattle is explained by the timing of slaughter relative to symptom development, not by actual differences in infection rates.
Supporting Logic: Since both cattle and chickens are exposed to the virus through contaminated feed, and since infected animals take more than a year to develop symptoms, and since chickens are brought to market within their first year while cattle live longer, the chickens are being slaughtered before symptoms can manifest. Therefore, the "very rare" observation of the disease in chickens reflects timing of observation rather than actual infection rates.
Clarification Note: The passage supports that chickens may actually contract the virus at similar rates to cattle, but this remains undetected due to early slaughter. The passage does not support any claims about chickens having natural immunity or resistance to the virus.
This choice discusses transmission from chickens to humans, which is completely outside the scope of our passage. The argument focuses on why we observe the disease less frequently in chickens compared to cattle, not on inter-species transmission to humans. We have no information about human transmission in the passage, so this cannot be supported.
This makes an absolute claim that there's 'no way' to determine infection before symptoms appear. While the passage tells us symptoms take more than a year to develop, it doesn't state anything about detection methods or testing capabilities. The passage is silent on diagnostic procedures, so we cannot support this broad negative claim.
This choice correctly identifies that the low observation of disease in chickens doesn't prove immunity. Since both cattle and chickens are exposed through contaminated feed, and chickens are slaughtered before the year-long symptom development period, the lack of observed disease in chickens could simply be due to timing rather than immunity. This directly follows from the passage's logic about exposure and timing.
This discusses transmission between infected animals of the same species, which goes beyond what our passage addresses. The passage focuses on disease observation patterns and timing, not on transmission dynamics between animals. We cannot infer anything about transmission capabilities from asymptomatic infected animals based on the given information.
This suggests the feed is probably not the only virus source. However, the passage doesn't provide any information about alternative sources of the virus. The argument assumes the feed is a significant transmission method but doesn't rule out or hint at other sources, making this inference unsupported by the given facts.