Table 1.

Stages of clinical reasoning applicable to veterinary medical education, using an example of a cow with Mycoplasma mastitis, having components of a population-level problem.

Stage	Activity/ Element	Example of Veterinary Medical Learner’s Synthesis of Information
1. Consider client ± patient situation	NA	Mrs Jane Do is an experienced dairy farmer and has presented Margery, a 5-year-old Holstein cow with recurrent mastitis in both rear quarters. Margery is otherwise ‘healthy’. Mrs. Do is very concerned about Margery as she is used as a ‘donor cow’ for embryo transfer.
2. Collect data	Presenting problem	Recurrent mastitis in both rear quarters.
	Health interview	Margery is a homegrown cow that had a previous bout of mastitis about 3 weeks ago in both rear quarters. As Mrs Do has an on-farm milk culturing system, she tried to isolate the causative pathogen/s, but the culture result was negative. She had no other recorded health problems throughout Margery’s life. Mrs. Do has purchased 10 cows from a producer who was selling their business, just over 3 months ago. The sale was due to the old shed and high herd-level somatic cell cows that were not controllable. Mrs. Do has purchased only cows that had high genetic merit, but no other history was available for these cows. The current milking herd consists of approximately 600 milking and 200 dry cows, in addition to 300 pregnant heifers and 2 bulls. Cows are milked twice daily through a rotary milking shed with 60 units. The milking machine is thoroughly washed after every milking cycle. Herd testing is carried out every month. The number of cows with increased individual cow somatic cell counts in the last two herd tests seems high. In the last two months, the bulk tank milk somatic cell counts and number of cows with clinical mastitis have started to increase in a progressive fashion, in comparison to historical data. Most cows with mastitis had signs in two or more quarters. By plating on selective media, the applicable on-farm culturing system allows for the identification of common mastitis pathogens from the groups of coliforms, staphylococci, and streptococci. No growth has been detected using the on-farm culture system. Additionally, there were three replacement neonatal calves with fever, head tilt, severe obtundancy, and poor response to antimicrobial treatment. These calves were euthanized on animal welfare grounds.
	Various examination steps	Environment and husbandry—no abnormalities detected (NAD). Margery’s clinical examination findings—Bright and alert. Except for the changes in the milk composition from both rear quarters, no other abnormal findings. Milk composition from both rear quarters—watery with small flecks in the first approximately 10 strips becoming milk-like with small flecks thereafter. No signs of increased heat, pain, or swelling of the affected quarters.
	Ancillary examination techniques/tests	California Mastitis Test (CMT) results—Both rear quarters: thick gel (+++). Front left quarter: light gel formation (+). Front right quarter: no gel (−). Double, aseptically collected milk samples were submitted for common bacterial pathogens culture from all quarters (individual sampling per quarter). Culture results—no growth after 72 h. Resubmission and request to culture for Mycoplasma spp. resulted in both rear quarters having heavy Mycoplasma spp. growth. The front left quarter also resulted in a light Mycoplasma spp. growth.
3. Analyze the data and 4. Identify problem/s ± Issue/s	Review data/Problem representation	Mrs Jane Do is an experienced dairy farmer and has presented Margery, a 5-year-old valuable Holstein cow, with recurrent mastitis in both rear quarters that have not grown common mastitis pathogens using the on-farm mastitis culturing system. Margery’s mastitis is of a mild character. No other abnormalities were detected in her, but the herd-level incidence of clinical mastitis and somatic cell counts progressively increased over the last two months.
	Review context	Mrs Do mentioned that Margery is used as a ‘donor cow’, meaning she is quite valuable and genetically superior. The client is concerned about Margery’s animal welfare and progressively rising somatic cell counts coupled with an increasing number of clinical cases at the herd level. Valuable cow for the client.
	Problem identification	Altered secretion from both rear quarters resulted in positive CMT. Culture identified Mycoplasma spp. as a causative pathogen. Increasing incidence of clinical mastitis. Increasing bulk tank somatic cell counts. Calves with suspected otitis, non-responsive to antimicrobial treatment.
	Recall knowledge	Exemplars/Illness scripts/Prototypes/Semantic qualifiers Mastitis is an inflammation of the mammary gland/s that is most commonly caused by bacterial pathogens. Based on the main characteristics of the causative pathogen, mastitis can be environmental or contagious. Based on the presentation, mastitis can be mild, moderate, severe, or subclinical (Figure 1). Diagnosis of clinical mastitis is based on the presence of clinical signs. Diagnosis of subclinical mastitis is based on the use of various tests detecting the pathogen or changes in the milk composition. Etiologic diagnosis requires identification of the causative pathogen.
	Interpretation	Recurrent mastitis in both rear quarters with no growth on traditional culture but positive on Mycoplasma spp.
	Discrimination	‘Margery does not present with generalized malaise.’
	Relating	‘Although Margery has mild mastitis, her overall demeanor does not seem to be affected.’
	Inferring	‘Margery’s mastitis is likely associated with the increased incidence of clinical mastitis on the enterprise, and to the progressively raising bulk tank somatic cell count. Based on the presented data, it seems that we are dealing with a contagious mastitis.’
	Matching	Mastitis in multiple quarters, often of a recurrent nature, that may be associated with otitis media and respiratory disease in other herd members is common with Mycoplasma spp. as a causative pathogen.
	Predicting	Even without treatment, Margery’s mastitis is likely to apparently self-cure in a few days, but the real cure is much lower.
5. Establish mutually agreed goals	NA	‘Margery’s wellbeing is marginally affected. The most likely diagnosis is Mycoplasma mastitis which is difficult or impossible to treat. As this form of mastitis is contagious, we agreed that the best course of action is to minimize the spread to uninfected cows by introducing milking segregation. However, if Margery’s mastitis does not self-cure in 3–5 days, we may consider drying her off or culling her. Are we all in agreement?’
6. Take action	NA	In this encounter, due to the contagious nature of the causative pathogen, the best course of action is milking segregation of all cows and milking them in the following order: (1) cows with low somatic cell count and no signs of clinical mastitis; (2) cows with high somatic cell count but no signs of clinical mastitis; and (3) cows with signs of clinical mastitis (milk discarded). Cows suspected of having subclinical and clinical mastitis will be regularly sampled and tested by culture or PCR for the pathogen. Additionally, all 10 points of the National Mastitis Council should be followed in detail [5]. To prevent the spread to calves, milk fed to calves must be pasteurized. Alternatively, calves can be fed with milk replacers.
7. Evaluate the outcome	NA	Margery’s mastitis apparently disappeared in two days. As her condition is non-treatable and self-cure rates for Mycoplasma mastitis are lower than for most forms of mastitis, the client may consider culling. Yet, her genetic superiority may prevent culling. If Margery does not self-cure, she may need to be used only as a ‘donor’ cow before culling and milking is not advisable. Additionally, Mycoplasma mastitis is of a contagious nature and does not respond well to dry cow treatment. This makes all cows infected with Mycoplasma spp. being a continuous source of infection for uninfected cows.
8. Reflection and new learning	NA	Mrs Do mentioned that Margery is used as a ‘donor cow’, meaning she is quite valuable and genetically superior. Culling as an option is unlikely to be easily acceptable by the client. The risk to other cows should be considered and explained to the client. The client should be aware that the eradication of the pathogen from the enterprise is not easy, and may take a few years of meticulous work, coupled with cooperative labor working with cattle.