Swellings Involving the Head
A number of specific conditions are limited to the head or neck. These are discussed below and some of them can be located with the aid of Figure 3.5.
Figure 3.5 Swellings involving the head or neck: (1) cheek abscess or cud retention, (2) salivary mucocele, (3) tooth root abscess, (4) bottle jaw, (5) thyroid gland, (6) thymus gland, (7) wattle cyst.
Retention ofa Cud in the Cheek
Contented goats frequently have a bulge in the cheek region during rumination. The swelling disappears as soon as mastication is complete or the goat is startled. If such a swelling persists and is found on careful digital examination to consist of a cud rather than a thickening of the cheek (abscess), neurologic dysfunction, a tooth problem, or some other condition interfering with mastication or swallowing should be suspected.
Tooth Problems
Absent, irregular, or abscessed teeth may lead to improper chewing and accumulation of feedstuffs or cuds between the dental arcade and the cheek. These problems are discussed below and in Chapter 10.
Facial Nerve Paralysis
Cud retention may indicate facial nerve paralysis, and thus should prompt a thorough neurologic examination (see Chapter 5). Deviation of the philtrum, drooling, inability to blink, and drooping of the pinna may also be present. Conditions to be considered in differential diagnosis include traumatic injury to the facial nerve, otitis media, listeriosis, and other lesions involving the brain stem. Of these, listeriosis should receive special consideration, because the disease is most apt to be successfully treated if clinical signs are limited to peripheral nerve dysfunction.
Salivary Mucocele
Painless swellings on the side of the face sometimes are cystic structures filled with saliva.
Anatomy and Physiology
The parotid salivary glands of the goat are roughly rectangular and extend from the ear to the bifurcation of the jugular vein. Each parotid duct runs subcutaneously across the lateral surface of the masseter muscle near its ventral border. It empties into the mouth via the parotid papilla, which is opposite the upper fourth premolar or first molar (Habel 1975). The mandibular salivary glands are triangular in shape. They lie deep to the parotid gland and caudal to the mandibular lymph node, along the medial side of the angle of the mandible. The mandibular ducts, which are less accessible to injury than the parotid ducts, go to the medial side of each sublingual caruncle. The monostoma- tic ducts of the sublingual glands open on the lateral side of each sublingual caruncle. Sialography can be performed (Tadjalli et al. 2002). In addition to these major paired glands, there are diffuse layers of salivary gland tissue in the walls of the mouth and pharynx.
The salivary glands of ruminants secrete continuously. The saliva is slightly alkaline, because of its high concentration of bicarbonate. The physiologic function of saliva is discussed in Chapter 10.
Etiology
Blockage or rupture of a duct can lead to formation of a salivary mucocele. Forceful restraint of the head of young kids against a metal brace during disbudding has led to mucocele formation. It is also important to avoid damaging the glands or the parotid ducts in surgical operations involving the head and neck, in particular drainage or extirpation of abscessed lymph nodes.
Painless fluid-filled cysts have been reported on the side of the face or in the submandibular region of young Nubian goats. These cysts were found to be lined by pseudostratified columnar epithelium containing goblet cells. Parotid salivary gland duct epithelium appears similar, and thus these cysts were presumed to be developmental anomalies (Brown et al. 1989). Figure 3.6 shows a 1-month-old Nubian kid that had fluid-filled cysts bilaterally at birth.
These cysts, which appeared to be outpocketings of a salivary duct, were removed surgically and the ducts ligated.Clinical Signs and Diagnosis
Aspiration of the soft, fluctuant, non-painful swelling should yield a clear, watery, or slightly blood-tinged mucoid fluid that is colorless and odorless. The pH level is higher than that of blood. Confusion with a tapeworm cyst over the mandible, as discussed below, might be possible (Ghosh et al. 2005).
Figure 3.6 Congenital salivary gland duct cyst in a Nubian kid.
Source: Courtesy of Dr. R.P. Hackett.
Treatment
Salivary cysts can be excised, as long as the caudal portion is ligated to occlude the parotid salivary gland duct. Excision of the gland itself is not required (Brown et al. 1989). Such swellings should not be lanced, because a chronic fistula and continuous loss of saliva may result. The discharge is not only esthetically displeasing; the loss of bicarbonate, which approaches 30-50 g/day in experimentally cannulated sheep, can lead to life-threatening acidosis.
Abscess
Subcutaneous abscesses on the head, as elsewhere on the body, may involve a variety of organisms, including C. pseudotuberculosis, Trueperella pyogenes, Escherichia coli, and staphylococcal and streptococcal species (Ashfaq and Campbell 1979b). Nocardia has also been isolated from chronic subcutaneous abscesses on the face and elsewhere on the body (Jackson 1986). An anaerobic staphylococcus has been associated with a herd outbreak of subcutaneous abscesses involving the head in goats in the Sudan (El Sanousi et al. 1989).
From Biting Cheek
When an abscess is located in the cheek, exactly where upper and lower molar teeth meet, the possibility of a selfinflicted injury with contamination by bacteria in the oral cavity must be considered. Filing of exceptionally sharp points on the teeth may be justified to avoid recurrence.
Manual restraint of a goat's head in such a way that skin of the cheek is forced between the molar arcades (as when teaching a kid to drink from a bucket) and tight halters should be avoided.From Other Wounds
Wounds in the skin or oral mucosa may result from puncture by thorny vegetation or from grass awns. Bite wounds by predators or more dominant goats also offer a portal of entry for pyogenic organisms. In general, identifying the exact microorganism involved is not important, other than for ruling out caseous lymphadenitis. Draining and then flushing the abscess with dilute iodine usually provide adequate therapy. Systemic penicillin or other antibiotic is given if the goat is systemically affected or the lesion is especially large.
Actinobacillosis is somewhat different, in that Actinobacillus Iignieresii causes multiple chronic, firm, nodular lesions, often with draining tracts in sheep. The lesions are located in soft tissues of the head or in the regional lymph nodes. The presence of small (less than 1 mm in diameter) granules in the pus is quite suggestive of actinobacillosis, but unfortunately they are not often seen. Confirmation requires culture of the organism. Sulfonamides, streptomycin (not available in the United States), and sodium iodide have been recommended for treatment; penicillin is not effective. The occurrence of actinobacillosis in goats has not been documented. The condition is commonly seen in sheep flocks free of C. pseudotuberculosis and can be mistaken for caseous lymphadenitis, resulting in unnecessary culling if cultures are not performed.
From Dehorning
Dehorning represents a special wound that may become infected and eventually develop into an abscess beneath the eschar from heat cautery or the bandage or scab from surgical horn removal. This condition is discussed below under sinusitis.
Tooth Root Abscess
As a sequel to periodontal disease (perhaps from feeding coarse hay or hay containing grasses with barbed awns), foreign material gets between the tooth and gum and an abscess may form around the root of a molar tooth.
In the authors' experience this occurs most often in the lower jaw and is accompanied by decreased hay consumption and difficulty cudding. The infection progresses until bony distortion of the ventral ramus is noted (Figure 3.7). The swelling is easily detected by comparing the thickness of the mandibles while palpating with the thumb and forefinger of each hand. This ventral swelling may break and drain pus. An oral exam (with xylazine tranquilization) should be conducted to identify obviously broken or loose teeth that need to be extracted. More typically, the tooth involved can only be identified with an oblique radiograph of the jaw. Some of these goats respond to repeated iodine
Figure 3.7 Tooth root abscess involving the mandible. Source: Courtesy of Dr. M.C. Smith.
flushing of the draining tract and three to four weeks of penicillin or florfenicol or some other antibiotic selected on the basis of culture and sensitivity. A pelleted hay product encourages feed consumption during the initial stages of therapy because extensive chewing is not required.
Although surgical extraction of the involved tooth has not been reported in the caprine literature (except for treatment of a septic mandibular dentigerous cyst; Miller et al. 1997), experience with other species suggests that this might be the preferred treatment if accomplished without fracture of the mandible. Oral extraction of a molar tooth would be very difficult (if the tooth is not loose) because of poor exposure, and consideration should be given to osteotomy of the lateral mandibular plate, as is described for llamas and small exotic ruminants (Wiggs and Lobprise 1994; Niehaus and Anderson 2007; Miesner et al. 2014). After the tooth is repelled into the mouth, a pack of dental acrylic will exclude food particles from the surgery site.
Actinomycosis
Lumpy jaw (Actinomyces bovis or other Actinomyces spp.) apparently is very rare in goats (Seifi et al.
2003; Oyekunle et al. 2010). Involvement of bone and the presence of sulfur granules raise the suspicion of this infection. Treatment is as for actinobacillosis, with five to seven days of streptomycin if available (10 mg/kg twice or three times daily) combined with oral iodides as a possible protocol. Daily subcutaneous injections of oxytetracycline at 20 mg/kg can be substituted. Important conditions to consider in differential diagnosis are tooth root abscess, osteodystrophia fibrosa, and invasion of the jaw bones by lymphosarcoma (de Silva et al. 1985; Craig et al. 1986; Guedes et al. 1998; Rozear et al. 1998) or some other neoplasm (Murphy et al. 2011).Osteodystrophia Fibrosa
A marked bilateral enlargement of the mandible has been reported in young (and occasionally adult) goats consuming mostly concentrate and thus having excessive phosphorus relative to calcium in the diet. The mandibles are soft (readily penetrated by a needle or knife) and the cheek teeth are rotated so that the crowns are directed toward the tongue (Andrews et al. 1983; Bandarra et al. 2011). Demineralization is evident on radiographs (Singh 1995). In advanced cases, it may be impossible to open the mouth. Spontaneous fractures may occur. Feeding a good hay (such as alfalfa, which is high in calcium) and restricting the grain should prevent this condition, which is discussed in more detail in Chapter 4.
A similar mandibular (and maxillary) osteodystrophia fibrosa has been observed in four goats on a long-term (472 days) feeding trial with Leucaena Ieucocephala. The calcium to phosphorus ratio was more than 6 : 1. The kidney, thyroid, and parathyroid were histologically normal, and occurrence of the condition was not explained (Yates et al. 1987). Chronic renal disease might result in similar bone lesions.
Bottle Jaw
The presence of fluctuant pitting edema in the intermandib- ular space of goats that are not obviously in heart failure should arouse the suspicion of endoparasitism (see Chapter 10). The edema results from hypoproteinemia, which follows blood and plasma loss caused by nematode infestations of the gastrointestinal tract and fluke infestations in the liver. Paratuberculosis also can cause severe enough hypoproteinemia to manifest as bottle jaw, as can renal disease. These conditions are discussed in Chapters 10-12.
Swelled Head of Bucks
Fighting bucks may develop severe edematous infections of the head in regions where Clostridium novyi is prevalent. Other clostridia including C. chauvoei, C. sordelli, and C. septicum may be involved. The swelling begins near the horns and eyes, but may extend down the face, neck, and chest. Tissues are full of yellow fluid and clostridia may be demonstrated on smear or anaerobic culture. Lymph nodes are swollen. The animal is lethargic and febrile. Death usually occurs within one to two days, unless the swellings are opened surgically to allow oxygenation and massive doses of antibiotics (penicillin) are given. Photosensitization (see Chapter 2) might appear similar, but does not spare the ears and is less rapidly fatal (King 1984). Bucks with a simple seroma or hematoma on the poll from fighting will not be systemically ill.
Deformation ofthe Cranium
An abnormal profile of the cranial bones suggests hydrocephalus in the neonate and sinusitis or parasitic cyst in the older goat.
Hydrocephalus
Occasionally kids are born with an obvious doming of the skull and congenital hydrocephalus. This is usually sporadic, with no known predisposing cause, although some kids congenitally infected with Akabane virus or Neospora caninum (see Chapters 4 and 13) have hydrocephalus. The hereditary lysosomal storage disease of Nubians, beta mannosidosis, is also accompanied by deformation of the cranium, and is discussed in Chapter 5. Kids with hydrocephalus should be euthanatized if neurologic abnormalities are severe enough to interfere with nursing or locomotion.
Sinusitis
Except in neonatal kids, surgical dehorning invariably opens the frontal sinuses, into which hay and other foreign matter may easily fall. If a scab closes the opening before any infection present is eliminated, it is possible for an abscess to develop that may eventually lead to softening and distortion of overlying bone. A history of open dehorning within the last six months would be suggestive. Careful percussion may demonstrate a relative dullness over the affected sinus. Radiographic evaluation is recommended if there is any doubt that the swelling is over the frontal sinus rather than the cranial cavity or tooth roots. Drainage should be established and the sinus flushed daily, after removal of any foreign material or necrotic bone.
Enzootic intranasal tumor and lymphosarcoma, as discussed in Chapter 9, can invade the sinuses and cause bony distortion of the face. Digital pressure on softened bone causes expulsion of a seromucous exudate from the nostrils when an enzootic intranasal tumor is present (de las Heras et al. 1991). Decreased airflow is detectable through the nostril on the affected side. A dorsoventral radiograph reveals the space-occupying nature of the tumor.
Coenurus cerebralis (Gid)
Coenurus cerebralis is the larval form of the canine tapeworm Taenia multiceps. It can form cysts in the parenchyma of the brain or on its surface in sheep and goats. Blindness or various other neurologic signs occur, depending on the exact location of the cyst. The overlying skull may bulge and soften, or even perforate. Where this sign is relied on for diagnosis it is reported to be common (Sharma and Tyagi 1975), although many affected animals show no outward changes in the skull. Insertion of an 18- gauge needle through the softened bone yields clear fluid under pressure, and sometimes the cyst can be extracted from the cranium by aspiration through a tube inserted via this needle. At least one goat has been cured by injecting Lugol's solution into the cyst. A more detailed discussion of this parasite is supplied in Chapters 5 and 6. The parasite may no longer be present in the United States.