Examples of diseases and conditions which can lead to hypokalaemia

(Tab. 3)

 

Examples of diseases and conditions which can lead to hyperkalaemia

(Tab. 4)

 

Chloride (Cl)

Chloride is one of the most important anions in the ECS. To a large extent, it is bound to sodium and present as common salt (NaCl). As a counterion of Na, it plays an important role in maintaining the water distribution between the ECS and the ICS, hence, in the plasma osmolality.

As a vital electrolyte, more than half of the chloride is found in the ECS (about 55%), approximately one third in the bones (about 30%) and only a small part inside the cells (about 15%).

 

Chloride fractions

Chloride is mainly taken in through common salt (sodium chloride) in food. It is excreted via the kidneys and regulated by the hormone aldosterone, which causes reabsorption of the anion if there is a lack of chloride (Fig. 1).

 

Example of diseases associated with an increase in serum chloride

(Tab. 5)

 

Examples of diseases associated with a decrease in serum chloride

(Tab. 6)

Dr. Anja Cölfen

Inorganic phosphorus (P)

The terms phosphorus and phosphate are used interchangeably in laboratory medicine. For clinical purposes, this is irrelevant because the phosphate content is measured as inorganic phosphorus. 85% of the phosphate is located in the bones in combination with calcium and 14% exists intracellularly. There, it is present as an anion or as a component of lipids, proteins and nucleic acids. 1% of the P content is located in plasma or in other body fluids, yet in most pathological conditions, the concentration in serum correlates with the phosphate content of the body. Renal reabsorption is an important indicator of the phosphate level in the serum. If phosphate absorption is increased or GFR is decreased, renal reabsorption is decreased. Renal reabsorption is regulated by fibroblast growth factor (FGF) and parathyroid hormone.

 

Examples of hypophosphataemia

(Tab. 3)

 

Hyperphosphataemia

Hyperphosphataemia lowers the concentration of 1.25(OH) vit D and increases the secretion of PTH and FGF. These hormones have a phosphaturic effet.

 

Examples of hyperphosphataemia (physiological in young animals)

(Tab. 4)

 

Magnesium

1% of the magnesium (Mg) is found in the extracellular fluid. The Mg fractions in serum and plasma are present as ionised magnesium, protein-bound magnesium, mostly to albumin, and complex-bound magnesium in form of salt. The skeletal system, the gastrointestinal tract and the kidneys regulate the magnesium concentration in the plasma. Magnesium depends on the albumin concentration and the pH value. If there is alkalosis, the Mg level is reduced by increased protein binding. However, a reduction may also be seen with normal serum levels. Magnesium has many different tasks: It is essential for electrolyte balance, energy metabolism (activation of ATP), neural conduction, protein synthesis, bone matrix formation and mineralisation of the skeleton as well as for cell division.

 

Examples of hypomagnesaemia

(Tab. 5)

 

Hypermagnesaemia

Except for severe CRI, hypermagnesaemia is unlikely to occur with adequate substitution.

Serum electrolytes and nutrition

When evaluating serum electrolytes, special attention should be paid to nutrition. Calcium is only ingested with the food through bones, bone meal and egg shells. Muscles and innards, vegetables and fruit are significantly lower in calcium. Ca deficiency in the diet results in increased PTH secretion. This leads to mobilisation of Ca from the bones and increased absorption from the intestine. In the long term, bone demineralisation develops and even bone deformation, particularly of the long bones, as well as other changes in the skeletal system. A typical sign is the so-called “rubber jaw”. Ca oversupply, on the other hand, which occurs much less frequently for nutritional reasons, leads to tissue calcification, stomach ulcers and impaired muscle contraction up to tetany. Severely disturbed bone metabolism, especially in the long bones, and increased urinary excretion of calcium are signs of Ca oversupply. Phosphate is present in many food products (meat, vegetables and fat). This means that phosphorus intake from food is usually sufficient. Phosphate is stored in the skeletal system and regulated by the kidneys. Food should have a Ca/P ratio of 2:1 or maybe 1.5:1. Inadequate supply, even inverse Ca/P ratios, are often seen in individual rations. Magnesium is mainly found in green vegetables, nuts, cereals, seafood and meat. But also drinking water, especially hard water, contains magnesium.

Conclusion

Concerning serum levels and nutrition, it is particularly important to note that serum levels in the normal range do not necessarily reflect a balanced diet. Serum electrolyte levels in the reference range do not imply that the ration sufficiently meets the needs for these parameters. A balanced ration calculation is required instead.

Dr. Anja Cölfen

Fresh specimen

For a fresh specimen, a pea-sized amount of fresh faeces is usually sufficient. With – ideally warm – physiological saline solution or water, a faecal suspension is prepared. For the microscopic examination, a drop is placed on a slide and covered with a cover glass. Testing from a smaller sample quantity is generally possible, but carries the risk of reduced sensitivity.

Yeasts, such as Cyniclomyces guttulatus, as well as protozoa (Tab. 1) and occasionally worm eggs can be detected very well in the fresh specimen.

One of the most frequent causes of diarrhoea is dysbiosis – a shift in the rather gram-positive intestinal flora towards more gram-negative bacteria, clostridia and yeasts. Causes are often of dietary origin (inappropriate feeding, resulting in a lack of crude fibres and/or excess carbohydrates), any kind of malpositioned teeth or even parasitosis. A first and quick indication of a dysbiotic condition is the increased occurrence of yeast (>15/visual field) at 100-fold magnification.

Although flagellates, such as giardia, can be diagnosed in fresh faeces, they are very rarely found. Such findings in fresh faecal samples are only conclusive in positive cases. A more suitable test procedure for this is the giardia ELISA.

Tape test method

The tape test method – perianal tape impression using adhesive strips – is a quick and simple test method which may as well be carried out on site. It is particularly recommended for the detection of oxyurid eggs and larvae (Passalurus ambiguus). Detection by flotation is often negative, as oxyurid eggs tend to sink due to their high density. Sometimes, however, larval fragments of Passalurus ambiguus can be found in the flotation.

Pooled faeces

A 3-day pooled faecal sample generally increases the sensitivity of the faecal analysis for parasites (except for flagellates). When submitting faecal samples from rabbits or guinea pigs, different test methods are available: flotation, sedimentation (SAFC method), bacteriological examination, giardia ELISA and PCR (pathogen specific).

Flotation

The principle of the flotation test is based on the fact that parasite stages with a low density are transported to the surface of solutions which have a higher specific gravity. In rabbits and guinea pigs, this test method is suitable for the enrichment of coccidian oocysts as well as for the enrichment of species-specific nematode and cestode eggs (Tab. 1) and can be carried out in the practice, too, using commercially available test kits.

Sedimentation

During sedimentation, parasite stages with a high density settle in the sediment of a lighter solution. With this test method, especially trematode eggs (Fasciola hepatica, Dicrocoelium dendriticum) can be detected in rabbits. To some extent, the detection of nematode eggs is also possible, although flotation is to be preferred here due to its higher sensitivity. Trematode eggs have not yet been described in guinea pigs.

Bacteriological examination

The culture of faecal bacteria provides information on the pathogenesis and allows for targeted treatment through the creation of an antibiogram. Rabbits and guinea pigs as herbivorous caecal digesters physiologically have a mainly gram-positive flora with several hundred different bacterial species, yeasts, anaerobes and protozoa. Pathogen differentiation with a subsequent creation of an antibiogram is advisable for them, especially in food-producing animals and if human pathogenic organisms are suspected, but is of little use in the typical cases of diet-induced dysbiosis.

Shifts towards a gram-negative intestinal flora should always be considered in the context of feeding mistakes and/or parasitosis. This is because the detection of a certain species of bacteria is no proof that it is the actual cause of diarrhoea – except for pathogenic bacteria (particularly toxigenic ones) (Tab. 2).

Polymerase chain reaction

Polymerase chain reaction (PCR) is a method for the detection of specific pathogens, such as Lawsonia intracellularis. The advantage is its high sensitivity, the disadvantage is that it must be known beforehand which pathogen to look for and that only a positive result confirms it. A negative result cannot completely rule out an infection.

Blood test

Diarrhoea in rabbits and guinea pigs may also have extragastrointestinal causes. Depending on the animal species, various causes need to be considered, such as organic, metabolic or toxic disorders as well as hypovolaemia or neoplasia (Fig. 1). A blood test (Rodent Profile incl. a complete blood count) covers almost all differential diagnoses and should thus be part of the routine diagnosis of diarrhoea if the previous faecal examination was negative.

During the haematological examination of dysbiotic patients and patients with diarrhoea, a so-called pseudo left shift (shift from lymphocytic to neutrophil blood count) is often seen. Here, too, a differential blood count can help in making a diagnosis. In guinea pigs, leukocytosis with lymphocytosis indicates lymphoma and eosinophilia indicates parasitosis as a possible cause of diarrhoea. Unfortunately, this is not the case in rabbits; they usually have aleukaemic lymphoma and do not show eosinophilia due to parasites. A blood test is also suitable to clarify organic-metabolic or endocrine causes of diarrhoea (e.g. hyperthyroidism in guinea pigs). Hepatopathies (GLDH, AST, ALT, bilirubin, bile acids, triglycerides, cholesterol) and nephropathies (urea, creatinine) as a cause of diarrhoea as well as electrolyte shifts (Na, K, P), protein losses (total protein, albumin) and/or blood losses (erythrocyte count, haematocrit, total protein, albumin, urea) can easily be determined.

A blood test may also be very helpful in serious conditions such as ileus or obstruction: The glucose level serves as a prognostic factor in this case. The higher the level, the more likely it is that ileus is the cause and the worse the prognosis.² If sodium is additionally considered in the interpretation, an even more precise prognosis can be made, because additional hyponatraemia doubles the mortality rate.³

Conlcusion

The faecal analysis combined with a haematological and clinical-chemical examination covers almost all the differential diagnoses of a diarrhoeal disease and can thus serve to initiate quick and targeted treatment.

Hormonal imbalances

Behaviour is regulated by a variety of hormones and hormonal interactions. Changes in a single hormone level can trigger profound behavioural changes.

Thyroid gland: Diseases of the thyroid gland frequently occur in dogs and cats. In dogs, both cause and symptoms differ with age. In young dogs, it is autoimmune thyroiditis which leads to behavioural changes, whereas in older dogs these changes are caused by follicular atrophy.

In young dogs, anxious or aggressive behaviour with hyperactivity and severe educational problems is often associated with thyroid dysfunction. If these patients really suffer from thyroid-related behavioural problems, these are due to initial episodes of autoimmune thyroiditis with fluctuating hormone secretions. The diagnosis is confirmed by measuring the T4 and TSH levels but, above all, by determining the thyroglobulin antibodies (TgAb) as well as T3- and T4-antibodies.

In older dogs, hypothyroidism is one of the most common known endocrine disorders. Some of the first changes that are observed are increasing reluctance to move and lethargy. As the function of the thyroid gland can be influenced by many other diseases, it is necessary to determine the T4 and TSH levels and to rule out other conditions in order to confirm the diagnosis.

The clinical signs triggered by hyperthyroidism in older cats (weight loss, hyperactivity) often lead to a quick diagnosis. Only rarely, hyperthyroid cats are apathetic. In most cases, measuring the T4 level in serum is sufficient; in uncertain cases, TSH can be measured.

Gonads/adrenal gland: Sex steroids are responsible for a complex system of behaviours. The castration of domesticated animals and, thus, the suppression of gonadal function is frequently performed and significantly influences the behaviour. Not only the reproductive ability but especially aggressive behaviour against conspecifics should be suppressed. In case of dominance problems, it is also expected that castration will make it easier to guide the dogs.

If the dog or the cat continues to show sexual behaviour despite being neutered, the question arises as to whether there is still some gonadal tissue present. Determining the luteinising hormone (LH) as well as steroid hormones and particularly the measurement of the anti-Müllerian hormone (AMH) level in both male and female animals can help to answer this question.

Endocrine neoplasms can also manifest themselves through behavioural change. In the early phase, this may even be the only clinical sign. Sertoli cell tumours cause male dogs to become attractive to other males and to behave more like being neutered due to increased oestrogen secretion. Granulosa cell tumours in female dogs can mimic the behaviour of a pregnant bitch with nest-building behaviour and carrying around soft toys if hormone secretion, especially progesterone, is low but constant. It is alarming for the owner that no previous heat was observed and, thus, a false pregnancy is unlikely.

Endocrine active adrenal tumours lead to various behavioural changes depending on the hormonal secretion pattern. While Cushing’s syndrome, which is common in dogs, is primarily associated with increased appetite up to allotriophagia, other tumours of the adrenal cortex are rare. A rather common tumour of the adrenal medulla is the catecholamine-secreting phaeochromocytoma. The permanently elevated level of catecholamine in the blood results in increased restlessness and anxiety in patients. Determining the catecholamines normetanephrine and metanephrine in blood plasma or the normetanephrine- and metanephrine-creatinine ratio in urine helps to confirm the diagnosis.

Neurotransmitters

Recently, clinical laboratory testing of dogs with behavioural problems has started to focus on the “happiness hormone” serotonin. Serotonin is a neurotransmitter whose effects in the CNS include the inhibition of fear and aggression. A lack of serotonin in the CNS therefore leads to fearful-aggressive behaviour. Although serotonin cannot cross the blood-brain barrier, low serotonin levels in the blood correlate with certain behavioural problems. This correlation has been confirmed by our own research (Fig. 2).

Therefore, measuring serotonin in serum is recommended for dogs with fearful-aggressive behaviour. In addition to food supplementation with tryptophan, treatment can be carried out with serotonin analogues or serotonin reuptake inhibitors. A return to normal behaviour can be expected after a few weeks.

Infectious causes

It is the tactic of some infectious agents to manipulate their host’s behaviour with the aim of being transferred to a new host more quickly. A typical example for this is an infection with the rabies virus. Fortunately, rabies only plays a very minor role in Germany. Nevertheless, it may be a differential diagnosis in animals from uncontrolled imports and should be considered if dogs are aggressive.

But even less dramatic and much more frequent infections can also lead to behavioural changes. Especially ectoparasites living in the fur or on the skin can lead to increased restlessness without causing massive itching at the same time. Infected hair can be sent in to identify the parasite.

Poisoning

The intake of foreign substances is another way in which unwanted behaviour can be triggered. Lead poisoning manifests itself in various ways with restlessness, agitation, increased barking or biting and depression. If the dog ingests nicotine through cigarette butts, it leads to agitation and hyperactivity. It also frequently happens that animals take drugs if the owner does not handle the drugs carefully. Depending on the drug and dosage, behaviour can vary and range from hyperexcitability to somnolence. A single intake of poison results in a sudden change in behaviour and, at a higher dose, is usually associated with further symptoms.

Genetic behavioural problems

Particularly in pedigree animals, there are various genetic defects that are associated with behavioural change. These include, for example, neuronal ceroid lipofuscinosis (restlessness, aggressiveness, anxiety), acral mutilation syndrome (paw chewing), glycogen storage disease (lethargy), necrotising meningoencephalitis (disorientation, head shaking, circling), dopamine transporter polymorphism (hereditary behavioural abnormality in Malinois dogs: reduced excitability, episodic aggression) and many more. The causative mutations have already been identified in numerous breeds, which is why the option of diagnosing hereditary diseases in pedigree dogs with behavioural problems should also be taken into account. Especially for dogs, we offer an extensive and constantly growing range of tests. For more information, see https://shop.labogen.com/

Primary laboratory parameters to be determined relating to the most common behavioural problems (Tab. 1).

(1)  Send in cooled (possibly frozen) and protected from light
(2)  Frozen EDTA plasma, urine acidified with HCI to pH < 2, send in frozen and protected from light
(3)  EDTA whole blood
(4)  Only possible from urine; always state clinical history.

Dr. Ruth Klein

Leishmaniasis

In cats, Leishmania infantum is most likely transmitted by sand flies (Phlebotomus spp.). Dogs are considered the main reservoir, but cats can also become infected. However, it is assumed that cats are more resistant to infections than dogs. The pathogenesis of feline leishmaniasis is unclear, just like the role of the cat in the transmission cycle of the pathogen.

In cats, infections are often subclinical. When clinical signs occur, mainly nodular and ulcerative skin lesions are seen as well as enlarged lymph nodes, weight loss and ophthalmologic symptoms. To confirm infection, quantitative serological tests such as IFAT should be carried out in cats. In case titres are negative or low, a parasitological detection method (e.g. PCR, culture, histology, cytology) should be used to diagnose the pathogen if there is a clinical suspicion as seroconversion of the pathogen may be delayed for years.

Ehrlichiosis

In Europe, Ehrlichia (E.) canis is transmitted by the tick Rhipicephalus sanguineus. In Germany, the vector can only survive temporarily within certain temperature ranges or as populations in buildings heated throughout the year. Case studies on infections with E. canis in cats are rare and the clinical picture is non-specific. A single positive antibody detection by IFAT most likely indicates a pathogen contact in an endemic foreign country.

Rickettsiosis/Mediterranean spotted fever

More than 20 species belong to the “Spotted fever group”, with Rickettsia conorii being the most important zoonotic agent in Europe. Rickettsia conorii is transmitted by ticks (Rhipicephalus sanguineus) and can cause clinical signs in dogs; its significance in cats is not clear.

Rickettsia felis is transmitted by fleas. Seroconversion occurs in cats after contact with infected fleas. Bacteraemia is assumed to be short, as cats with confirmed antibodies usually had negative PCR results in blood. Antibody detection was often positive in cats in which several vector-borne infectious agents were found. This also reflects what is known about pathogen detection in dogs or in human medicine.

Dirofilariasis

Diroflaria (D.) immitis (heartworm) is a pathogenic species in cats, while D. repens, as the causative agent of subcutaneous dirofilariasis, also plays an important role as a zoonotic agent. Both pathogens are transmitted by mosquitoes. Prevalence in cats is only about one tenth of that in dogs. In cats, infections with D. immitis may be self-limiting, however, there may also be fatal courses with sudden death and clinical signs such as shortness of breath, coughing and vomiting. Yet, cats are more resistant than dogs and only occasionally develop transient microfilaraemia. Since larvae are only temporarily detectable in the blood and/or the number of larvae is below the detection limit of the D. immitis antigen detection test or the Knott’s test, false negative results often occur in cats. Heat treatment of the serum before performing the test increases the probability of pathogen detection.

We offer this method after prior consultation. Furthermore, a cardiac ultrasound should be performed to detect worms in the pulmonary artery as well as in the right atrium and the right ventricle of the heart. Diroflaria repens can cause skin lesions such as subcutaneous nodules.

Severe courses with itching, pustules, ulcerations and exfoliative dermatitis are rare. Microfilaria PCR has a low sensitivity in cats. If pathogen detection is positive, it should be followed by species differentiation to decide on the treatment (Fig. 2).

Summary

In cats with the appropriate medical history, vector contact and the respective clinical signs, vector-borne infections should also be considered in the differential diagnosis. Some vector-borne infections are probably underdiagnosed in cats. The role of the cat as a reservoir host and the clinical relevance of many vector-borne infections are not yet sufficiently understood. Preventive measures such as vector control throughout the year with suitable acaricidal and insecticidal preparations are also recommended for cats. The prepatent period of dirofilaria and leishmania is long. In case of negative test results within six months after import or return to Germany, it is thus recommended to repeat the test at the time when the cat has exclusively been in Germany for at least six months.

Chlamydia felis is an obligate intracellular bacterium and a common cause of acute and chronic conjunctivitis. Symptoms on the eye also include hyperaemia of the nictitating membrane and ocular discharge. However, keratitis and ulcerations are rather uncommon. If they occur, it indicates the involvement of feline herpesvirus. In some cases, infection with FHV1 is accompanied by fever, inappetence, weight loss and respiratory symptoms, and in pregnant animals, abortion may occur. According to the literature, young cats under 9 months of age are most frequently affected, which is confirmed by our data. Transmission occurs through close contact, as the bacterium cannot survive outside the host. Shedding of the pathogen can last up to 60 days, occasionally, an even longer, persistent infection is possible. In individual cases, C. felis can be transmitted to humans and cause conjunctivitis. PCR is the most sensitive method for detecting C. felis.

Mycoplasmas are considered part of the normal microflora of the upper respiratory tract. Nevertheless, Mycoplasma felis plays an important role as a pathogen in feline conjunctivitis. Mycoplasmas are less frequently involved in lower respiratory tract infections, although they can also cause severe pneumonia in individual cases. Only very rarely, M. felis shows zoonotic potential in immunocompromised people. It is difficult to culture mycoplasmas; that is why here, too, detection by PCR is the method of choice.

Contrary to dogs (kennel cough complex), Bordetella bronchiseptica only plays a minor role in cats. The bacterium is a primary pathogen that colonises the ciliated epithelium of the host. It is rarely found in the lower respiratory tract of cats, if so, mainly younger animals are affected. Still, every coughing cat should also be tested for B. bronchiseptica. Bordetella can be transmitted from dog to cat and a zoonotic potential cannot be excluded. In addition to swabs of the nasal mucosa and the oropharynx, bronchoalveolar lavage can also be examined. Bacterial culture as well as PCR are suitable methods. However, performing an antibiogram is only possible after culture. If the pathogen is detected in the lavage sample, it is seen as proof of infection.

Diagnosis

In general, PCR is considered the standard method for the detection of the causative agents of feline upper respiratory disease complex. Conjunctival, oral and/or pharyngeal swabs are suitable sample materials for the detection of viral infections, mycoplasma and chlamydia. Ocular swabs should always be taken BEFORE fluorescein or rose bengal are applied. As chlamydia replication is obligate intracellular, they cannot be detected by routine bacteriological methods. Infections with Bordetella bronchiseptica are rather rarely found in cats; a fast and sensitive PCR detection is possible here as well. Since there are often bacterial co-infections, especially in cases involving the eyes, but also in chronic respiratory tract infections, an additional swab with transport medium should be sent in for bacteriological examination including the creation of an antibiogram, in order to be able to initiate a suitable local and/or systemic therapy. For the diagnosis of feline upper respiratory disease, antibody detection is less useful, because many cats are vaccinated or have had pathogen contact as kittens.

Since most infections are often acute as well, it is usually the pathogens which can be detected at the onset of the disease, but not the antibodies that are produced in the further course of the disease. In the literature, it is stated that 80% of upper respiratory tract infections in cats are, above all, caused by FHV1 and FCV. Laboklin offers various PCR profiles for the detection of the most common pathogens of feline upper respiratory disease. Over the past years, in the Respiratory Profile I (FCV, FHV1, chlamydia, mycoplasma, B. bronchiseptica), mycoplasma was found to be the most prevalent pathogen (in up to 50% of the Respiratory Profiles that were examined), followed by calicivirus and herpesvirus (each in about 20% of cats examined). Infections with chlamydia (7 – 9%) and Bordetella (2 – 3%) play a minor role. In the vast majority of cases, Bordetella was found in mixed infections (94.7%), there were only 2 cases (5.3%) in which it was found as single infection.

In total, there were hardly any differences in the occurrence of individual pathogens in each of the years of the evaluated period between 2011 and 1018.

In 2018, 951 (50.1%) of the 1897 total samples for the Respiratory Profile 1 (cat) were positive for mycoplasma, 305 (16.1%) for FHV1, 333 (17.6%) for FCV, 128 (6.7%) for chlamydia and 38 (2%) for B. bronchiseptica (Fig. 1). Of these 1897 total samples, 450 (23.7%) showed mixed infections with two or more causative agents of feline upper respiratory disease (Table 1). Mixed infections of mycoplasma and FCV/FHV1 were most common, followed by infections with mycoplasma and chlamydia and mixed infections with both viruses (Fig. 2).

Table 1: Number of mixed infections in the Respiratory Profile I (cat) in 2018 (total number of samples n = 1897)

Table 2: Mixed infections and frequency of occurrence of the individual pathogens of feline upper respiratory disease (FCV, FHV, chlamydia, mycoplasma, B. bronchiseptica) in 2018

Intestinal dysbiosis in dogs

Our own studies, which compared the copy numbers of important anaerobic bacterial markers for intestinal dysbiosis in dogs with chronic diarrhoea and a clinically healthy control group by means of quantitative real-time PCR, show clear differences (Fig. 2a). Particularly noticeable is a significant reduction in the anaerobic, carbohydrate-digesting intestinal flora, the saccharolytic bacteria (Faecalibacterium prausnitzii, Blautia spp., Turicibacter spp.). An important function of these groups of bacteria is to metabolise fibre components in the food that are difficult to digest to short-chain fatty acids such as acetate, propionate and butyrate. They serve as the main source of energy for the enterocytes in the colon and are essential for the maintenance of the muscosal barrier. Regarding their diet, dogs are omnivores. Their digestive system and metabolism are therefore adapted to a high carbohydrate content in their food. This is why a shift in the intestinal flora towards proteolytic bacteria (e.g. Clostridia, Proteus, Klebsiella) and with reduced numbers of saccharolytic bacteria is not a physiological state but a sign of intestinal dysbiosis.

… and in cats

Although the anatomical similarities of the gastrointestinal tract suggest otherwise, the composition of the intestinal microbiota is very different in dogs and cats. Figure 2b shows a comparison of the intestinal microbiome of clinically healthy dogs and cats. There is a significant underrepresentation of saccharolytic intestinal microorganisms in cats (E. coli, Fusobacterium spp., Turicibacter spp.). As in dogs, the reason for this is probably the diet. Domesticated cats are obligatory carnivores and need protein-rich animal tissue to meet their energy needs.

Therefore, their digestive system and metabolism are adapted to a higher protein and lower carbohydrate content in the food. The resulting nutrient supply in the intestine is an enormous selective advantage for proteolytic bacteria and a disadvantage for saccharolytic ones. A eubiotic status of the microbiome in a healthy feline gut is thus characterised by a lower number of saccharolytic and a higher amount of proteolytic bacteria.

Disorders of the intestinal flora in cats

Just as in dogs, there are also measurable differences in the composition of the intestinal microbiome between clinically healthy cats and animals with chronic diarrhoea. A comparison of the microbial dysbiosis markers of the two groups shows that the number of saccharolytic intestinal bacteria is significantly increased in cats with chronic diarrhoea compared to clinically healthy animals. This could mean that cats depend less than dogs on microbial fermentation products of saccharolytic bacteria. A shift in the bacterial balance towards saccharolytic intestinal bacteria is therefore more characteristic of a dysbiotic situation in the intestine.

Similarities and differences

Despite the differences between dogs and cats regarding their diet and intestinal microbiota, there seem to be certain intestinal bacteria in both species that are essential for maintaining intestinal homeostasis. An example of this is Faecalibacterium prausnitzii. This is a strictly anaerobic gram-positive bacterium with important anti-inflammatory and protective effects on the intestinal mucosa. Reduced copy numbers of this intestinal bacterium are a clear indication of intestinal dysbiosis in dogs and cats.

The opposite seems to be true for bacteria of the species Fusobacterium. In dogs, viable counts of Fusobacterium spp. are significantly higher in the clinically healthy control group than in animals with chronic diarrhoea; in cats, in contrast, this is only true in the affected group (Fig. 2b). It is not clear whether these are different bacterial counts of the same species or of different bacterial species. The environmental conditions in the dysbiotic cat gut may possibly promote the growth of fusobacteria with pro-inflammatory potential, which could favour the occurrence of clinical symptoms.

Indications to test for dysbiosis

Even though there are significant differences in the gastrointestinal tract between dogs and cats, the indications for a micro-ecological analysis of the intestinal microbiome are identical in both species. They include:

• gastrointestinal disorders of unknown origin, e.g. chronic diarrhoea and flatulence
• digestive disorders, exocrine pancreatic insufficiency
• recurrent parasitoses (e.g. Giardia)
• food intolerances and allergies
• status monitoring after antibiotic treatment

A micro-ecological analysis of the intestinal flora can support the differential diagnosis and provide valuable new therapeutic approaches. However, only microbiological-cultural methods are often used for such tests, for example when determining the bacterial counts of enterococci, bifidobacteria or lactobacilli. For several reasons, these tests are not sufficiently suitable for a diagnosis. On the one hand, with less than 1%, only a very small proportion of the intestinal bacteria is detected. And on the other hand, when comparing the copy numbers of these bacteria in both dogs and cats, there are no significant differences (Fig. 4). This is also true when comparing clinically healthy animals and animals with chronic diarrhoea.

The microbiologically-based, culture- independent analysis of dysbiosis, in contrast, tests and quantifies essential, non-culturable bacterial markers for intestinal dysbacteria. If reference values are adapted, which consider the differences between the normal flora of dogs and cats, intestinal dysbioses can be detected quickly and reliably.

Treatment of intestinal dysbiosis

Changing to low-fat, highly digestible food while  taking into account the individual nutritional requirements is the most important step in the treatment of disorders of the intestinal flora. The risk of inflammatory responses and intolerance reactions can be reduced by avoiding raw food and allergen-rich food ingredients. In case of acute diarrhoea, faeces-forming, toxin-binding substances such as aluminosilicate clays or humic acids can effectively relieve the symptoms.

Ground psyllium husks added to the food have a prebiotic effect and promote the growth of the protective flora in a natural way. Additionally, in combination with water, they release mucilage that slows down the intestinal transit in case of diarrhoea and facilitates defaecation in case of constipation.

Only when the acute symptoms have subsided, the use of microbiological therapeutics is indicated. Attention should be paid to always use probiotics in a suitable dosage form (enteric-coated capsules or tablets, microencapsulated powder), high bacterial counts (> 10⁹ CFU per dose) and with a high diversity of bacterial species involved.

For all gastrointestinal disorders associated with chronic diarrhoea, oral immunotherapy with autovaccines is also a suitable therapeutic option. Through the increased production of specific antibodies and a supplementary supply of mucosa-nutritive metabolites, the mucosal barrier is supported and the immune defence is strengthened. Its use is recommended both in acute condition and as a cure to prevent recurrence.