Bovis ISSN 2398-2993

Neonatology: fever

Synonym(s): pyrexia

Contributor(s): Mike Reynolds , Ash Phipps

Introduction

  • Body temperature is an important parameter routinely measured as part of a clinical examination.  
  • Pyrexia (fever) is defined as an elevation in core body temperature and in the neonatal calf can be taken as a temperature greater than 39.5°C.
  •  Signs:
    • Clinical signs may vary widely depending on etiology.
    • If multiple cases of pyrexia are present, appropriate biosecurity protocols should be instigated due to the high likelihood of an infectious disease.
  • Diagnosis:
    • Initial investigations should include:
      • A detailed history.
      • Clinical examination.
    • Full hematology may be beneficial at this stage:
      • A low white cell count with a left shift and presence of band neutrophils in indicative of a severe infection.
    • Microbial testing of blood samples - searching for antibody or antigen.
      • If there is any doubt as to the causal organism of a herd problem, then it will be necessary to identify the pathogen which may involve further blood testing or other sampling (swabs, BAL etc).
      • Blood testing may require paired serology and careful interpretation. However, positive results will justify the time and expense, so as to target management practices and treatment appropriately.
  • Treatment:
    • The specific treatment plan will depend on the pathology identified and is beyond the scope of this article.
    • Whilst a diagnosis is being pursued in the critical patient, symptomatic treatment should be employed, including intravenous fluid therapy and nonsteroidal anti-inflammatories as indicated.
    • Attempts should be made to identify the cause of the pyrexia prior to administering antimicrobial therapy.  
  • Prognosis: dependent upon etiological agent.

Pathogenesis

Etiology

  • In neonatal calves bacteria or viral infections, excitement, seizure activity and environmentally induced hyperthermia can all cause pyrexia.

Predisposing factors

General

  • Being born into unhygienic conditions.
  • Concurrent infection.
  • Poor nutrition.
  • Poor housing (bedding, ventilation, drafts etc).
  • Stocking density.
  • Mixing of age groups.

Specific

Pathophysiology

  • The thermoregulatory center in the hypothalamus is responsible for regulation of core body temperature, ensuring the core temperature is tightly controlled. This is based on information received from peripheral and central thermoreceptors and allows normal body homeostasis to occur.  
  • The central temperature receptors are found in the anterior hypothalamic-preoptic area.
  • The anterior hypothalamic-preoptic area and the peripheral receptors transmit signals into the posterior hypothalamic area, which activates autonomic and behavioral responses to regulate body temperature. 
  • After initial pathogenic stimulation, fixed and circulating monocytes and macrophages produce pyrogenic cytokines which induce the febrile response in the neonatal animal.
  • Cytokines such as Tumor necrosis factor and Interleukin-1 travel via the circulatory system where they induce the production of arachidonic acid and its metabolism to prostaglandin E2 by the cyclooxygenase (COX)-2 pathway which leads to a higher set point in the hypothalamic thermoregulatory center.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

Other sources of information

  • Fecteau M E & White S L (2015) Alterations in Body Temperature. In: Smith B P Large Animal Internal Medicine. 5th Edition. Chapter 4, pp 31-39.
  • House J K, Gunn A A, Chuck G, McGuirk S M (2015) Initial Management and Investigation of Neonatal Disease. In: Smith B P Large Animal Internal Medicine. 5th Edition. Chapter 19, pp 286-301.


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