Parelaphostrongylus tenuis and other parasitic diseases of the ruminant nervous system.

There are many parasites that affect the ruminant central nervous system. Clinical signs can vary dramatically based on the location and mobility of the parasite. Clinical disease can occur due to the physical presence of the parasite and the resulting host immune response or the toxin produced by the parasite. Differentiating the cause of disease is particularly important because prognosis,treatment, and subsequent control measures vary dramatically depending on the disease process. This article focuses on the pathogenesis,treatment, and control of some of the more common parasitic diseases of the ruminant central nervous system.     

Congenital defects of the ruminant nervous system.

Abnormalities of the nervous system are common occurrences among congenital defects and have been reported in most ruminant species. From a clinical standpoint, the signs of such defects create difficulty in arriving at an antemortem etiology through historical and physical examination alone. By first localizing clinical signs to their point of origin in the nervous system, however, a narrower differential list can be generated so that the clinician can pursue a definitive diagnosis. This article categorizes defects of the ruminant nervous system by location of salient clinical signs into dysfunction of one of more of the following regions: cerebrum, cerebellum,and spinal cord. A brief review of some of the more recognized etiologies of these defects is also provided. It is important to make every attempt to determine the cause of nervous system defects because of the impact that an inherited condition would have on a breeding program and for prevention of defects caused by infectious or toxic teratogen exposure.     

Clinical examination of the ruminant nervous system.

Practical and rapid physical examination techniques that allow the clinician to neuroanatomically localize the site of disease to the cerebrum,cerebellum, brainstem/cranial nerves, or spinal cord/peripheral nerves are described. The physical examination methods discussed in this article can be performed easily and quickly and do not require any specialized or expensive equipment to perform.     

Infectious diseases of the central nervous system.

Neurologic disease is seen commonly in cats, with infectious causes accounting for 30-45% of cases. However, since a specific infection cannot be identified in 12-40% of these cases, it is essential that we try to understand these cases better in the hope that we can eventually identify the cause(s), and so determine how best to treat and/or prevent them.     

Clinical pharmacology of nervous system diseases.

The well-developed defense barriers of the CNS and the expense of drug therapy limit the pharmacologic options for the treatment of neurologic diseases in horses. New approaches to controlling inflammation in the CNS are improving the outcomes of bacterial meningitis. The appropriate treatment of EPM remains controversial. More research is needed to evaluate the pharmacokinetics and pharmacodynamics of drugs in the CNS of the horse. Behavioral pharmacology has become fashionable in human and small animal medicine, but it needs to be evaluated for the potential of unethical use in performance horses.     

Viral diseases of the rabbit.

Viral disease in the rabbit is encountered infrequently by the clinical practitioner; however, several viral diseases were reported to occur in this species. Viral diseases that are described in the rabbit primarily may affect the integument, gastrointestinal tract or, central nervous system or maybe multi-systemic in nature. Rabbit viral diseases range from oral papillomatosis, with benign clinical signs, to rabbit hemorrhagic disease and myxomatosis, which may result in significant clinical disease and mortality. The wild rabbit may serve as a reservoir for disease transmission for many of these viral agents. In general, treatment of viral disease in the rabbit is supportive in nature.     

Assessment of the ruminant digestive system.

Evaluation of the gastrointestinal system of ruminants is a logical progression of investigation and elimination. Important aspects of the animal's history pertinent to the gastrointestinal system are described. A systematic, comprehensive technique for physical examination is presented with emphasis on the digestive and lymphatic systems. Examples of potential signs of disease are provided for each body section.     

Assessment of the ruminant respiratory system.

With practice, complete use of the methods of this assessment: history, detailed examination of the head and neck, cough induction, chest auscultation and percussion, and chest auscultation following forced rebreathing can be completed within 10 minutes. The examination can provide a great deal of new information regarding the respiratory system that would go undetected on a more general physical examination. In cases in which the diagnosis is still in question or requires confirmation, this will also enable the optimal use of appropriate ancillary tests, as described in the article on ancillary testing for the respiratory tract elsewhere in this issue.     

Therapy of diseases of ruminant intermediary metabolism.

Diseases of intermediary metabolism include ketosis and fatty liver of dairy cattle and pregnancy toxemia of ewes. These conditions occur when there is a failure of the homeostatic mechanisms regulating the mobilization of fats and the conservation of carbohydrates. The therapeutic approach is to reestablish the normal homeostatic patterns of fuel utilization. Suppression of excessive ketogenesis is the most important factor in reestablishing homeostasis. Ketogenesis can be suppressed by a number of therapeutic agents that act either by suppressing the mobilization of fatty acids or by inhibiting the transport of fatty acids into the hepatic mitochondria, the site at which fatty acids are converted to ketone bodies. Useful therapies include bolus glucose infusions, glucose precursors, and glucocorticoids.     

Viral diseases of ferrets.

Distemper and rabies vaccination are highly recommended because of the almost invariable fatal outcome of these conditions. Vaccination should constitute an important part of a ferret's preventative medicine program. With the current and anticipated development and licensing of new vaccines, practitioners are invited to gain awareness of the latest vaccine information. Establishment of a practice vaccination protocol with regards to the site of administration of rabies and distemper vaccines is paramount to document any future abnormal tissue reactions. Influenza is the most common zoonotic disease that is seen in ferrets. Although it generally is benign in most ferrets, veterinarians must take this condition seriously. The characteristic continuous antigenic variation of this virus may lead to more virulent strains; the recent emergence of avian influenza virus outbreaks; and the increased susceptibility of elderly, young, and immunosuppressed individuals.     

Nutritional and metabolic diseases involving the nervous system

This article will discuss eight diseases that alter normal nervous system function: hypovitaminosis A, water deprivation/salt toxicity, ammonia toxicosis, hypomagnesemia, hypocalcemia, nervous ketosis, hepatoencephalopathy, and rumen metabolic acidosis.     

Viral diseases of companion birds.

Many viruses definitively cause disease in our companion birds, whereas other viruses have been implicated or associated with typical clinical signs. Some families of viruses that have been discovered in mammals have not been associated with disease in birds. It is imperative to perform a necropsy on any birds that die--whether a pet, aviary, or display bird, and despite the fact that other diseases may be present--because viruses can occur concurrently, especially when immunosuppression is present. Also, it is imperative to use available vaccines to decrease and control the incidence of these diseases, as has occurred in the canine and feline pet populations.     

Ancillary testing for the ruminant respiratory system.

With greater use of a wide variety of diagnostic tools, such as transtracheal washing, respiratory endoscopy, chest radiography, thoracic ultrasonography, blood gas analysis, and lung biopsy, veterinarians are gaining tremendous insight into pathogenic mechanisms of the ruminant respiratory system. We have available many diagnostic aids; some fairly simple and inexpensive, others highly sophisticated and presently at far greater cost than justifiable on most individual food animals. Some methods recently developed, such as same-day viral particle detection in BAL samples,6 have tremendous potential for rapid and accurate diagnosis in ruminant pulmonary medicine. Undoubtedly, future research in this area will provide an ever widening array of powerful and rapid diagnostic aids to deal with respiratory disease of ruminants.     

Assessment of the reproductive system of the male ruminant.

Physical examination requires very little equipment or expense and is an effective means of obtaining valuable information concerning fertility. Thorough evaluation of the reproductive system provides important information often unattainable by any other means. Disease processes, congenital abnormalities, injuries, management errors, and many other factors can be identified. No segment of the examination should be overlooked, as each part is important. The time invested in evaluating the male reproductive system is rewarded with a more complete and accurate assessment of the breeding male.     

Ancillary tests for assessment of the ruminant digestive system.

This article reviews the ancillary tests that are available to evaluate disease and function of the gastrointestinal system. Procedures and tests such as abdominocentesis and peritoneal fluid cytology; rumen fluid analysis; abomasal pH and pepsinogen; upper digestive tract endoscopy; ultrasonography and radiology; hematologic and biochemical assessments; cytology, culture, and histopathology of aspirates; serology, liver function tests and biopsy; exploratory laparotomy; fecal examination; and microbiology are described.     

Viral respiratory diseases

An overview of the more commonly encountered viral diseases of the dog and cat is presented. The reader is acquainted with the principles of antiviral therapy and the drugs that have been studied for use in animal viral respiratory diseases. An update on vaccination principles and guidelines is provided.