Behavioural changes secondary to organic diseases are relatively common and justify a careful clinical examination during a consultation for behavioural problems (Fig. 1).
In the light of the model proposed by P. Pageat, the diagnosis of a behavioural disorder is a differential diagnosis, not a “hold all” diagnosis when an organic disease cannot be identified. An organic disease should be particularly suspected when:
- a behavioural disorder appears abruptly or evolves rapidly without apparent cause;
- there is rapid exploitation of the aggressive behaviours;
- phobias appear unexpectedly, with no traumatic cause, in an adult dog;
- there is worsening of already present phobias characterized by symptoms that suddenly become “very productive”;
- the animal’s symptoms do not fit into a well-defined clinical picture or there is inconsistency in the origin of the behavioural disorder.
The veterinarian should suspect the presence of an organic disease, whose symptoms mimic a behavioural disorder, when: (i) it is not possible to make a nosographic diagnosis (name the disease), but only a functional one (the presence of a pathological state such as phobia, anxiety, depression, dysthymia and so on); (ii) the symptoms shown by the animal appear to be “inconsistent” with the normal behavioural pattern of the species under examination; and (iii) the symptoms appear “unexpectedly”, with no history of prior behavioural disorders. In clinical practice, aggressive behaviour in the dog represents a non-pathognomonic sign of a pain disorder.
AGGRESSIVE BEHAVIOUR AND PAIN
According to K. Overall, aggressiveness can be an appropriate or inappropriate response to pain. In extreme conditions, biting may be the only resource left to an animal and in such cases the phase of intimidation is absent. A wounded dog may growl, snap or bite when moved because it is in pain. Pain secondary to arthritis can also trigger pain-induced aggressiveness: the victims are often children between 18 and 36 months old because they play roughly without motor coordination. Fights between dogs, if they cause wounds, can teach the animal on the losing end to be frightened or show fear-elicited aggression towards the aggressor.
When pain-elicited aggressiveness is triggered even by a light touch it is considered inappropriate. Indeed, biting should be the last form of canine communication, not the first. K. A. Houpt and K. Overall agree concerning pain-elicited aggressiveness. Furthermore, since pain can induce aggressive behaviour, it is easy to understand that physically punishing a dog because it is aggressive can worsen the animal’s undesired behaviour rather than improve it. According to C. Mège, E. Beaumont-Graff, C. Béata, C. Diaz, T. Habran, N. Marlois and G. Muller, since pain causes environmental modifications and changes in social relations, it can elicit or unmask behavioural disorders:
- Phobias: of the veterinarian, clinic staff, other dogs. When the pain is related to a bite, it induces fear or aggressiveness on the occasion of new contacts. Owners play a decisive role in the establishment of the process, avoiding all contact with other dogs for the fear of a new bite;
- Anxiety: this is generally intermittent anxiety with irritation-elicited aggression triggered by contact with a painful area. The aggression is exploited very rapidly because the appetitive (intimidation) phase disappears. The aggressive behaviour can persist also after the disappearance of the pain;
- Depression: pain can induce chronic depression which it is not then possible to eliminate only with analgesic treatment, for example in elderly dogs;
- Altered relations: the social situation changes because the dog becomes the object of the owner’s attention and is granted various privileges. The interspecies hierarchy can also be disturbed.
- Rituals: attention focused on a sore or painful area can trigger the development of attention-seeking rituals once the pain has passed (licking a paw, crying).
P. Pageat believes that the unexpected onset of a particular sequence of irritation-elicited aggressive behaviours in a dog that has never had relational problems with its entourage should raise the suspicion of aggression triggered by pain (acute or chronic). The sequence is that of a dominated dog: the intimidation phase is characterized by a low position, bent limbs, body turned slightly to one side, head and neck held towards the posterior part of the body – a hypocritical dog that bites without daring to make eye contact -, ears flattened backwards, dilated pupils, muffled poorly audible growl, multiple bites inflicted by throwing the head forward several times – not very harmful bites with the incisors -, fleeing, running away with body held close to the ground, flexed limbs, tail between the legs, and continued growling, towards a resting place or hideaway. The perceived pain can modify the reactive status of the animal and can lead to the development of a behavioural disorder, the Syndrome of “reactive aggressiveness” to pain. The signs can include:
- Hyperaesthesia: lowered threshold for the perception of pain, indirect organic manifestations (tachycardia, tachypnoea, panting). The noradrenergic system is involved;
- Avoidance: the animal avoids other dogs and members of the family. At first this behaviour involves the “fussiest” people, those who cuddle the animal a lot or groom it. When the animal is approached it adopts an aggressive demeanor (only in the phase of intimidation);
- Licking: gate control (competition between pain impulses and tactile impulses) or activation of the nociceptive fibres that control the pain response, with participation of beta-endorphins;
- Hypervigilance: the animal is always alert; sleep is reduced;
- Memorisation of the event preceding the painful situation (for example, an approaching hand, staring at one part of the animal’s body);
- Emotional anticipation;
- Disappearance of activities that act as positive reinforcement, such as playing.
Any irritation or pain is able to trigger sequences of irritation-induced aggression. Some individuals develop aggressive responses progressively, with increasing frequency and ever weaker association with the nociceptive situation. Such dogs have never shown any aggressive behaviour in the past and have been well included in family life. The first aggressive events occur unexpectedly and surprise the entourage. The person most frequently bitten is the one who has always had the best relationship with the dog and who takes care of the animal (grooming, washing). At the beginning the animal growls when approached by some people, particularly those who gesticulate and move brusquely or in an uncoordinated manner (children, handicapped subjects, elderly, very active people). Owners report that the dog is threatening but does not know clearly what it is doing: a stage of irritation-induced intimidation can be recognized in the dog that perceives itself as dominated.
After numerous episodes of this type, initially triggered by abrupt approaches or painful handling, it can be noted that the aggressive events become more frequent and, in particular, are elicited increasingly rapidly. The success of the irritation-elicited aggressive behaviour reinforces the behavioural response, increasing the probability of further irritation-induced aggression. At this stage the simple fact of moving into a trajectory even vaguely in the direction of the dog is sufficient to act as a trigger. Sometimes only talking to the animal or looking at it can provoke growling (anticipation phase). The condition evolves with the development of a phobia (of a specific person or category of people) which, once established, will be stable because of exploitation of the aggressive behaviour.
The disappearance of the painful condition does not resolve the problem; this can mislead the veterinarian who may think that the irritation-elicited aggression is a sign of a persistent organic disorder. In all stages, owners report that the aggressive crises are preceded by a change in the animal’s glare, with wild eyes reminiscent of a mad animal. This is the consequence of mydriasis. The clinical picture evolves, culminating in a bipolar dysthymia. The condition is, therefore, divided into a reactive state, of secondary hyper-aggressiveness, and a dysthymic one.
Suggested readings
- BERNARDINI M, Neurologia del cane e del gatto, Poletto editore, 2002, Gaggiano (Mi);
- COLANGELI R, GIUSSANI S, Medicina comportamentale del cane e del gatto, Poletto editore, 2005 Gaggiano (Mi);
- DAMINT S, BEATA C, (2005) Endocrinology and behaviour, About Hierarchy, Behaviour and Internal Medicine ESVCE, Marseille 8 – 9 october;
- DODDS WJ, (2004) Behavioral issues and thyroiditis: theory and case review. Proceedings American Holistic Veterinary Medical Association;
- DODMAN NH, SHUSTER L, Farmacologia comportamentale veterinaria, Masson s. p. a., 2000, Milano;
- FATJO’ J., MANTECA X. (1999) “Problemas de comportamiento en perros y gatos”. Dal: Seminario Iberoamericano de Comportamiento en Perros y Gattos, Univ. de Ciencias Aplicadas y Ambientales (U.D.C.A), Facultad de Ciencias Agropecuarias, Carrera de Medicina Veterinaria - Universtad Autónoma de Barcelona (U.A.B.). 4 e 5 Novembre 1999, Santa Fe de Bogotà, D.C;
- FERRIERE C, Eduquer un chien sourd, La communication, collection Zoopsychiatrie, 2005, Solal Editeur;
- GIUSSANI S, Perte de la vision et modifications comportementales chez les carnivores domestiques, Mémoire pour l’obtention du diplome de Vétérinaire Comportementaliste del Ecoles Nationales Vétérinaires, 2002 Nantes;
- HOPKINS S.G., Schulbert T.A., Hart B.L. (1976) Castration of adult male dogs: effects on roaming, aggression, urine making and mounting;
- MEGE C, BEAUMONT – GRAFF E, BEATA C, DIAZ T, HABRAN T, MARLOIS N, MULLER G, Patologia comportamentale del cane, Masson s. p. a ed EV s. r. l., Milano/ Cremona, 2006 prima edizione;
- Neilson J.C., Eckstein, R.A., Hart B.L. (1997) Effects of castration on problem behaviors in male dogs with reference to age and duration of behavior. J Am Vet Med Assoc 1997 Jul 15;211(2);
- O'Farrell V, Peachey E.. Behavioural effects of ovariohysterectomy on bitches. J Small Anim Pract. 1990;.
- OVERALL KL, La clinica comportamentale del cane e del gatto, C. G. Edizioni Medico Scientifiche s. r. l., Torino, prima edizione italiana;
- PAGEAT P, “La patologia comportamentale del cane” – Edizione Le Point Veterinaire Italie Milano 2000;
- SALMERI, K.R., BLOOMBERG, M.S., SCRUGGS,S.L., SCHILLE, V. (1991) Gonadectomy in immature dogs: effects on skeletal, physical, and behavioural development. J. Am. Vet. Med. Assoc.