CAHFS Connection - April 2026

Managing Editor: Kerry Ballinger 
Design Editor: Lucy Gomes 
Contributors: Cassie Powers, Emma Torii, Francisco Uzal, Javier Asin Ros, Karyn Bischoff, Patricia Blanchard, Roberto Olivares

General

New World Screwworm: 
New World Screwworm is not currently present in California or the United States; however, recent detections in northern Mexico, including Tamaulipas, underscore the importance of continued vigilance and early reporting. 

Here’s What to Watch For:
NWS infestations occur when adult flies deposit eggs in open wounds or mucous membranes (Fig 1). Larvae hatch and feed on living tissue, leading to progressive tissue damage. Clinical signs may include:

• Non-healing or worsening wounds
• Presence of larvae (maggots) within wounds
• Foul odor and discharge
• Increased irritation, abnormal behavior, or decreased productivity
• Higher risk in navel sites of neonates, surgical wounds, and untreated lesions

Early detection is critical, as undiagnosed cases can facilitate spread through animal movement. Suspect cases should be reported immediately to your local CDFA Animal Health Branch District Office and herd veterinarian. CAHFS is always available to receive samples and/or carcasses for diagnostic work up.

Here’s What It Will Look Like If Detected:
If NWS is identified in the United States, response actions will be rapidly implemented to contain and eradicate the pest. These may include:

• Establishment of an infested (control) zone with a minimum 12.4-mile (20 km) radius around the detection
• Implementation of surveillance zones extending outward up to approximately 124 miles (200 km)
• Movement controls and inspection requirements for animals leaving affected areas
• Requirement for treatment and veterinary clearance prior to movement, except for direct-to-slaughter movements under specific conditions

These measures are designed to limit spread while supporting continuity of agricultural operations.

Avian

Teratoma was the cause of death in a three-year-old, Brahma rooster noted to have peracute illness for <24 hours before being found dead. On gross examination, the coelomic cavity was markedly distended with yellow, clear, watery fluid, and had a large, ovoid, 14 x 9 x 9.5 cm mass replacing the right testicle. On histology, the mass was consistent with a teratoma. Teratomas are rare in animals, and in chickens have most commonly been reported in testicles and ovaries. Teratomas are most commonly benign, although when very large, such as in this case, they can cause the death of the chicken by compressing vital organs.

Avian mycobacteriosis was diagnosed in a 6-year-old hen with a history of delayed crop emptying, cachexia, leukocytosis, and a mottled liver with multifocal 1mm to 3mm in diameter, poorly demarcated white nodules. Microscopically, the liver had granulomas with intralesional acid fast bacteria (Fig. 2). These findings are consistent with avian mycobacteriosis, a chronic, debilitating bacterial infection, caused by Mycobacterium avium, which was detected in this case. This condition is transmitted via contaminated feed and/or water. M. avium can infect humans and poses a zoonotic risk; however, serovars found in birds and humans are typically different. Nonetheless, precautions should be taken to avoid human exposure to infected birds.

^{Figure 2: (Left) Liver with multifocal white nodules.  (Right) Microscopic view of the liver demonstrates acid fast bacteria (pink spots) within hepatocytes.}

Bovine

Epizootic Bovine Abortion (EBA) was diagnosed in a third trimester aborted bovine calf. On gross evaluation, the liver was markedly enlarged with rounded edges (Fig. 3). On microscopic evaluation, over 60% of the liver was necrotic and thymic lesions were compatible with EBA. High levels of antibodies against Pajaroellobacter abortibovis, the agent of EBA, were detected in fetal fluid by ELISA. EBA is a severe, tick-transmitted disease causing late-term abortions or weak calves in cattle grazing in California. It is reported to cause 10–50% pregnancy loss in naïve first-calf heifers.

Bacterial pneumonia was diagnosed in a one-month-old bull calf. On gross evaluation, cranio-ventral lobes were diffusely firm, mottled dark pink to red, with rare pus-filled white nodules. The surface of affected lobes was covered by a mat of fibrin (Fig. 4). Microscopically, there was fibrinosuppurative bronchopneumonia and pleuritis. Trueperella pyogenes and Mannheimia haemolytica were isolated, and Mycoplasma sp. (not M. bovis) was identified on PCR. These pathogens are frequently isolated together and are part of the bovine respiratory disease complex (BRD). BRD is a major health issue in cattle worldwide, caused by a mix of bacterial and viral pathogens, host factors, and environmental stresses. Clinical signs include ocular or nasal discharge, increased respiratory effort, and coughing.

Equine

Chronic selenosis was diagnosed in a horse with a history of brittle hooves. Deep horizontal cracks in hoof walls (Fig. 5) were seen clinically.  The blood selenium concentration was 0.66 ppm, more than twice the upper limit of the reference values (0.16 to 0.28 ppm). A major contributing factor to clinical selenosis in the horse is groundwater contamination. In this case, well water contained 1.4 ppm selenium. Water for livestock should not contain more than 0.05 ppm selenium.

Choledocholithiasis led to chronic cholangiohepatits in an 11-year-old male Warmblood horse. At necropsy, the most significant findings were jaundice and severe dilation of the common bile duct, which was almost completely obstructed by a yellow-to-green gallstone measuring 4-cm in diameter, which was compressing the major duodenal papilla (Fig. 6). The liver had multifocal white to yellowish areas. Histologically, there was fibrosis and inflammation of the common and major bile ducts. The liver showed moderate bridging fibrosis with inflammation, primarily affecting the portal tracts, moderate bile duct hyperplasia, and cholestasis. 

Small Ruminants

Campylobacter jejuni abortion was diagnosed in two male aborted, caprine fetuses from a farm that had at least 40+ abortions over a six-week period in a herd of 1150. Both placentas were bright red with multifocal yellow mucoid patches on the surface of the placentas (Fig. 7). On microscopic evaluation the placentas had multifocal inflammation and necrosis with colonies of bacteria compatible with Campylobacter spp (Fig. 8). A large number of Campylobacter jejuni were isolated from placenta and liver cultures of both animals. Two earlier fetuses also had Campylobacter jejuni isolated. This organism causes infectious abortion primarily in late gestation through the ingestion of contaminated feed, water, or aborted materials. Sheep, goats, and cattle are most often affected. It is a significant cause of abortion storms, resulting in stillbirths, weak kids, and retained placentas.

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