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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 be a part of the shelter's reported annual statistics. (An example is provided in Table 3.1). The shelter whose data appear in the table included the incidence and prevalence of major infectious diseases in its facility, mortality due to natural causes, and the number and percentage of euthanasias for medical reasons. This type of table provides a snapshot of the status of disease in the shelter, provides data to justify allocating funds for medical‐related goals, and summarizes progress toward improving the population's health on an annual basis. The medical staff should monitor common diseases or those associated with particular goals more frequently for timely identification of concerning trends (see the section on frequency of review, interpretation and communication).

Table 3.1 Annual medical profile in an adoption guarantee shelter.

Source: L.J. King, National Animal Health Monitoring System in the USA: a model information system for international animal health, Rev. Sci. Tech. Off. Int. Epiz., 1988, 7 (3), 583–588.

Disease	Number in Cats	Prevalence (%) in Cat	Number in Dogs	Prevalence (%) in Dogs
Coccidiosisa	106	24.7 (106/429)	81	15.2 (81/533)
Giardiasisa	36	8.4 (36/429)	51	9.8 (51/533)
Sarcoptic Mangea	–	–	37	8.6 (37/435)
Heartwormsb	–	–	162	9.3 (162/1746)
FeLVb	30	0.91 (30/3310)	–	–
FIVb	112	3.4 (112/3310)	–	–
Disease	Number in Cats	Incidence (%) in Cats	Number in Dogs	Incidence (%) in Dogs
URTD/CIRDc	637	18.3 (637/3484)	106	4.8 (106/2227)
Mortality (all causes)	55	1.6 (55/3484)	18	0.81 (18/2227)
Euthanasias for	216	6.2 (216/3484)	31	1.4 (31/2227)
medical reasons	0	–	–	–
● Treatabled	216	6.2 (216/3484)	31	1.4 (31/2227)
● Non-treatable

^a Animals positive for this organism among those tested with signs possibly associated with this disease.

^b Animals positive for this organism among those tested during the intake examination.

FeLV, feline leukemia virus.

FIV, feline immunodeficiency virus.

^c Disease that developed among the shelter animals while they were in residence in the shelter.

URTD, feline upper respiratory tract disease.

CIRD, canine infectious respiratory disease, also known as kennel cough.

^d Could be treated in the future with additional resources.

One issue complicating the collection of surveillance data is the failure to reach a diagnosis. For this reason, some software programs enable shelters to retrieve both “diagnoses” and “clinical signs” (check your software). From a disease‐surveillance standpoint, a diagnosis is preferable, but since a specific diagnosis is often not possible in shelters, recording and monitoring important clinical signs can be helpful. An unusual frequency of diarrhea might prompt the collection and submission of samples for diagnostic testing and identify, for example, an outbreak of giardiasis. Sometimes, the level of uncertainty of diagnosis is incorporated into disease data. For example, some studies incorporate case descriptors such as “possible,” “probable” or “confirmed” or “presumptive” vs. “confirmed” for diagnoses and incorporate these levels into their analyses. It can be helpful to have data regarding both diagnoses and signs, particularly when diagnoses are suspect, or the shelter wishes to monitor disease severity. If both signs and diagnoses are collected, they should be in separate data fields to avoid double counting.

To achieve consistency of data recording among staff over time, shelters need written descriptions of each of the diseases they include in the surveillance system. Staff members require training regarding those definitions and the importance of adhering to them. For some diseases, this is relatively easy. A diagnosis of feline leukemia virus (FeLV), for example, is based on a positive result on a commercially available, validated test; for other diseases, such as canine infectious respiratory disease (also known as kennel cough or CIRD), defining cases is more difficult, as respiratory signs alone rarely establish a definitive diagnosis. In these instances, a “working definition” of the disease can be used (as is often true during outbreak investigations) or the incidence of certain clinical signs may be monitored. Despite the difficulty, if no attempt is made to standardize the grounds for a diagnosis or create a working definition, it is hard (if not impossible) to interpret changes in disease frequency. The key is to standardize as much as possible what staff diagnose as a particular disease or identify as a clinical sign. The definitions need not be perfect, only consistently applied.

The collection of the date of the first diagnosis is essential to mark the onset of each new case so that incidence measures can be calculated for specific time periods. For diseases that can occur more than once in an individual animal (e.g. upper respiratory tract infections), only the first episode during a particular timeframe is counted as a new or incident case. If the medical team has an interest in reoccurring illnesses, the rate of second occurrences can be calculated and reported separately. If second (or other) occurrences are monitored during a time period of interest, the denominator includes only animals with a first occurrence in that timeframe. Fortunately, since most animals do not reside in most shelters long enough to experience second infections of most diseases, the rate of second infections is usually ignored. An exception may be in sanctuaries.