has also been hampered by shelter software that has been slow to facilitate entry and retrieval of the necessary data.
Summary metrics relating to disease surveillance, animal flow and capacity (housing and staffing) are discussed in this chapter to encourage shelter veterinarians to incorporate the use of these metrics into their population healthcare plans. As these metrics are used more extensively, other influential measures can be added.
3.2 Disease Surveillance
Disease surveillance is an integral component of managing and minimizing disease in public health and preventive medicine programs for livestock (Anderson 1982; Horstmann 1974; King 1985; Langmuir 1963). William Farr is credited with formalizing the principles of human disease surveillance beginning in the mid‐1800s in England. In the 1950s (during the height of polio outbreaks) in the United States, the Centers for Disease Control and Prevention (CDC) began formal surveillance programs for human communicable diseases (Langmuir 1963). It was not until the mid‐1980s that the Animal and Plant Health Inspection Service (APHIS) took the lead in developing a national surveillance program for diseases of U.S. livestock species (King 1985).
Routine disease surveillance requires quantification of disease frequency, descriptions of disease distribution among subgroups of animals, analysis and interpretation of data. Formally, disease surveillance is defined as (i) the ongoing systematic collection, orderly consolidation, analysis and interpretation of health‐related data in populations, and (ii) the prompt dissemination of this information to the people who are in a position to act on that data (Nelson and Williams 2007). Disease surveillance plans can include non‐infectious disease, but this chapter will focus on infectious disease.
3.2.1 Importance of Disease Surveillance
Knowing the nature and extent of disease occurrence in shelter populations enables veterinarians to:
assess population health in quantitative terms
set objective and measurable disease‐related priorities
identify outbreaks
plan and monitor the effectiveness of preventive and control measures
rapidly identify “new” diseases/conditions
justify grant proposals, and
clearly communicate the health of their populations to interested constituencies (e.g. Boards of Directors, funding agencies, community).
The basic metrics of interest in disease surveillance in shelters are measures of morbidity (frequency of illness such as incidence), and mortality (frequency of death). Recommended definitions of these metrics for use in animal shelters have been discussed (Scarlett et al. 2017a). An incidence rate is defined as the number of newly diagnosed cases of a particular disease divided by the number of animals that could develop that disease in a specified period. This fraction is usually multiplied by 100 and expressed as a percentage. By comparison, prevalence refers to the percentage of cases of a particular disease that are present in a particular population at a given time. In this chapter, the terminology “frequency of disease” is used to encompass the disease incidence or prevalence, as well as death resulting from or euthanasia that occurs because of a particular disease. One of these terms (e.g. incidence) is used when the discussion pertains to that metric alone.
If disease incidence is increasing, it is important to ascertain why and to intervene to reduce its occurrence. An increase in disease is usually associated with a breakdown somewhere in the shelter's health‐management protocols or signals the need for additional ones. Quickly identifying the possible causes of increased incidence is essential to maintaining population health. Even when the disease incidence is stable, quantifying the endemic level of diseases facilitates discussions of which diseases have priority for special attention (e.g. prevention, additional funding).
When discrepancies in the frequency of disease occur by host (e.g. kittens vs. adults), location (e.g. holding wards vs. adoption wards) or time of year (e.g. spring vs. fall) factors, these differences are often clues to underlying causes and/or additional steps that may need to be taken. They can indicate the need for new protocols, highlight breakdowns in current protocols, or suggest where and how a “new” disease agent entered the shelter and spread. The clues should lead to the development of hypotheses explaining the cause of the increased frequency, the precipitating event(s), and any factors supporting transmission in the shelter (if applicable). This knowledge then becomes the basis for preventive and control measures. If these measures are effective, disease rates decline, and recommendations can be made to prevent future increases in disease incidence. If rates fail to decrease, then protocols/initiatives are revised, and new approaches are instituted and evaluated.
Comparing the frequency of disease over time in a shelter or among shelters should be done thoughtfully. Interpretation of the differences in rates (or lack thereof) must always consider other explanations for what was observed. For example, comparisons of incidence rates before and after implementation of control measures can be a powerful means to assess the success and magnitude of the measures' effectiveness. However, changes in season affecting the age of entering animals or overcrowding due to an unanticipated seizure, for example, may explain the absence of an effect on disease rates, and not represent the failure of control measures. It is often necessary to consider ancillary information when interpreting any comparison. Similarly, demonstrating low incidence rates achieved in some shelters against those whose disease rates are high can be motivating. If done without thought, however, comparisons can also be discouraging (and unfair) if circumstances that can't be changed (e.g. characteristics of entering animals) between shelters are quite different.
Effective surveillance programs require good individual animal identification, a medical records system, a clear understanding of why surveillance is important, agreement on which diseases to include, clear definitions of those diseases, prompt disease reporting, incentives to report, and a management plan for affected animals. Regular timely analyses, clear surveillance reports, the ability to interpret and utilize those reports, and the dissemination of data to pertinent parties are essential. Protocols should be developed (e.g. documenting what to enter, when and by whom) to enhance the likelihood that diseases are identified, and pertinent data are entered consistently and completely.
3.2.2 Clear Objectives
Before initiating a disease surveillance program, clear objectives for the program should be outlined. The objectives must reflect the priorities of a shelter, be realistic, and be widely understood. Objectives could include, for example, quantifying the incidence of feline upper respiratory disease by host (e.g. age group, source) and time (season) factors, implementing appropriate control measures, and assessing the effectiveness of those measures.
3.2.3 Diseases/Signs to Surveil
One of the first steps in establishing a disease surveillance program is to create a list of the infectious diseases/signs that the medical staff believes are important to monitor. The focus should be on diseases/signs that are common (but could be reduced), particularly problematic (e.g. ringworm), or that are related to other medical goals (e.g. reducing time to recovery) of the shelter. The list should be short and manageable, with a focus on monitoring data that are likely to influence thinking and actions. Attempting to monitor too many diseases can overwhelm staff and lead to incomplete, inaccurate, or inconsistent data. It is better to collect and monitor data well for a few important diseases than to attempt to monitor many diseases and do it poorly; other diseases can always be added later. Once the list is established, the usual frequencies (endemic level) of those diseases should be calculated. (Note that some shelters develop an initial list and calculate the frequency of each disease, and then use the list to help decide which diseases to ultimately include in their surveillance program).
An annual medical profile is helpful in summarizing the yearly occurrence of disease for the shelter staff, the board of directors and other constituencies. The medical profile should