What a non-negative screen means

A non-negative Brucella canis antibody screen means your dog needs further interpretation and testing. It does not, by itself, establish infection. Ask your veterinarian which laboratory ran the screen, which confirmatory test follows, and whether that step is already underway. At Cornell’s Animal Health Diagnostic Center (AHDC), non-negative Canine Brucella Multiplex samples automatically undergo Canine Brucella Slide Agglutination/AGID II testing. Other laboratories use different pathways. Cornell’s screening and confirmation policy.

Serial testing means using a screening result to decide whether a more specific follow-up test is needed. Screening can produce nonspecific reactions, so a reactive result needs confirmation rather than an immediate assumption that the dog is infected. Equally, a negative result may need repeating when exposure was recent. The laboratory report, exposure history and veterinary assessment belong together. Iowa State’s explanation of serial testing.

Contact the veterinary team promptly for precautions while results are pending. B. canis can infect people, so suspected infection also matters to the staff handling specimens and to household members. Ask for a specific plan covering contact with other dogs, breeding or movement plans, and handling bodily fluids. Report the result before another appointment so the clinic can prepare. CDC veterinary guidance.

Keep the original report, including the test name and any interpretation comments. A telephone message saying “positive for Brucella” leaves out information needed to track the next step. Ask whether that message refers to an initial screen, a follow-up antibody result, or direct detection by PCR or culture. Those results answer different questions.

Track the Cornell screen and confirmatory result

Cornell’s published pathway separates routine screening from regulatory submissions. The following ledger shows the stages to track; “reflex” means the laboratory performs the follow-up after a qualifying screen, without waiting for a separate screening visit. It does not mean that the screen and confirmation are the same assay. Cornell’s May 2022 pathway announcement.

The multiplex measures antibodies against PO1 and BP26 using fluorescent beads. Cornell estimates sensitivity above 95% from parallel testing of more than 1,500 diagnostic samples against its own Slide Agglutination/AGID II combination. That is a laboratory estimate against an antibody-test comparator, not a promise that every infected dog will test positive. Cornell multiplex protocol.

Cornell reports specificity above 99% for its Slide Agglutination/AGID II combination testing. That figure does not describe the multiplex screen alone and is not the probability that an individual dog is infected after a positive result. The veterinarian still interprets the sequence in context. Cornell confirmation specificity.

For clinic planning, Cornell requests 2 mL of canine serum in a red-top tube, shipped overnight on an ice pack. This is a serum requirement, not a 2 mL whole-blood requirement. Veterinary staff should use the laboratory’s submission instructions; owners should arrange collection through the clinic. Cornell specimen requirements.

Use the laboratory’s received date as the starting point when discussing its reporting interval. Ask the clinic to distinguish shipping time, time awaiting confirmation and the time needed to relay the final interpretation. The published intervals are expectations rather than guaranteed delivery dates. If a breeding or travel deadline depends on the result, confirm the submission route before relying on that deadline.

A useful follow-up note has a few entries: the accession number, received date, screen result, whether confirmation is pending or complete, the final interpretation, and who will call you. A preliminary result and a completed interpretation can otherwise sound identical in a brief message. Recording the stage makes the next conversation more precise without asking an owner to interpret the assay.

Cornell’s announcement also contains a fee effective in May 2022. Obtain a current quote from the clinic or laboratory, including shipping and any additional testing, rather than budgeting from that historical amount. Ask what is included in the ordered service and what would require another authorization.

How other laboratory pathways differ

Cornell’s canine health page confirms that the previously common Zoetis D-Tec CB rapid slide agglutination kit was discontinued. That makes the actual test name and performing laboratory especially useful details to request. The discontinuation does not mean all point-of-care testing disappeared or that all laboratories now use Cornell’s multiplex. Cornell’s canine brucellosis overview.

Sources for the laboratory comparison: KSVDL diagnostic options; Iowa State Brucella testing; Montana testing options.

RSAT is a rapid slide agglutination antibody test. Adding 2-mercaptoethanol creates 2-ME-RSAT, which reduces nonspecific IgM reactions but can reduce sensitivity. Iowa State calls an RSAT-positive/2-ME-negative result suspect because cross-reactivity and early infection are both possible. A discordant result therefore needs interpretation over time, not an assumption that either test automatically cancels the other. Iowa State’s suspect-result explanation.

AGID II is agar gel immunodiffusion using cytoplasmic antigen. It is an antibody confirmation method; PCR seeks bacterial DNA, and culture seeks the organism itself. These methods are complementary. A negative direct-detection result may occur when bacterial numbers are low or bacteria are intermittently present in blood. Merck Veterinary Manual diagnostic overview; AGID II method in the 2025 study.

KSVDL’s older overview reports roughly 71% sensitivity for RSAT and 32% sensitivity/100% specificity for its confirmatory 2-ME RSAT. It also describes PCR detecting 2 CFU/mL, an analytical detection limit rather than a percentage of infected dogs detected. These lab-specific figures should not be used as a universal ranking. Confirm the method and current service details when ordering. KSVDL’s test-specific estimates.

Ask whether the next step uses the existing specimen, requires a new collection, or involves referral elsewhere. Do not assume every laboratory automatically runs every available confirmatory test. A result can remain unresolved because another test is pending, because another sample is needed, or because a repeat collection must wait for a more informative date. Those are different reasons for delay.

What the 2025 assay study can and cannot show

A 2025 US comparison distributed 56 banked serum specimens to 12 laboratories. Against 2-ME-RSAT, the VMRD B. ovis ELISA had about 97% sensitivity and 79.3% specificity; Bionote lateral flow had 90.6% and 95.8%; VMRD IFA had 87.5% and 87.5% in Table 1. The ELISA sensitivity differs slightly between abstract and table (96.8% versus 96.9%); the abstract also gives an inconsistent IFA specificity, so the IFA value here follows Table 1. LeCuyer and colleagues, 2025.

The study lacked culture or PCR status for those dogs. Its estimates compare antibody assays, not known infected and uninfected field populations. Specificity fell below 90% against AGID II and multiplex considered separately, not a combined reference standard. The authors support follow-up with a more specific test after a positive screen. These percentages cannot give an individual dog’s infection probability or a kennel’s prevalence.

Retesting depends on exposure and the first test

Antibody tests depend on the dog developing a detectable response. Cornell’s protocol says this usually takes at least 3–4 weeks after infection and can take 8–12 weeks. Its canine health overview warns about false negatives during the first three weeks. A recent negative therefore needs to be read alongside the date of possible exposure. Cornell seroconversion timing; Cornell early-negative caution.

Several published intervals appear in the sources, but they serve different situations. Iowa State recommends resampling suspect and initially negative animals in the involved group after 4–6 weeks. Montana recommends isolation and retesting after 30–60 days for suspect cases. In one South Carolina investigation, an 8-week follow-up was recommended for exposed household dogs. These are contextual examples, not a single national schedule. Iowa State retesting; Montana case management; South Carolina investigation.

Give the veterinarian a dated exposure history: introduction to a kennel, contact with a known positive dog, breeding, or reproductive illness. If the date is uncertain or contact continued after the first sample, say so. Ask which event starts the proposed retest interval, what the repeat test is intended to resolve, and what precautions apply until then.

A scheduled retest is different from a promise of clearance on that date. Ask what would happen after each possible result: another negative, a persistent reactive screen, or a new positive confirmatory result. That discussion helps owners and kennel managers plan follow-up without making breeding, adoption or movement decisions from a calendar entry alone.

Suspect, probable and confirmed are jurisdiction-specific

Montana’s definitions illustrate why the exact result and the official case category must be distinguished. The examples below are selective, not a complete reproduction of its thresholds. Symptoms and antibody levels can also affect classification. Montana case definitions.

An AGID-supported antibody result can therefore be “probable” under this state framework even when a laboratory describes its antibody testing as confirmatory. Clinical interpretation and regulatory classification are related tasks with different purposes. Ask the veterinarian which term is being used in the report and which authority decides the applicable case status.

Montana has quarantine authority but says individual cases confined to private homes are not routinely quarantined. Its guidance includes serious disposition recommendations, including euthanasia, with lifelong quarantine and sterilization as an alternative for confirmed cases. Decisions require the veterinary team and relevant officials; this example cannot determine another state’s requirements.

Also check that a Brucella test is appropriate for B. canis. KSVDL explicitly says its BAPA test detects smooth Brucella species and does not detect B. canis. Iowa State’s discussion of BAPA/FPA referral to NVSL concerns that smooth-species pathway. It should not be read as proof that every non-negative B. canis sample follows the same federal confirmation chain. KSVDL species distinction; Iowa State’s separate testing sections.

Reporting, movement and household exposure

The Merck Veterinary Manual describes B. canis as not nationally reportable in the US but reportable in many states. CDC directs veterinarians to local reporting rules, state animal health officials and local health departments. Ask who is making any required report and which instructions apply to this dog. Waiting for a final laboratory interpretation should not become a reason to ignore local reporting or exposure advice. Merck reporting overview; CDC reporting advice.

An old import notice can explain why destination-specific checking matters without establishing today’s entry rules. Wisconsin’s September 19, 2016 bulletin described an import permit and a negative brucellosis test within 30 days for sexually intact dogs obtained at out-of-state auctions. That is a dated example for a defined group of dogs. Confirm current destination requirements with the veterinarian and animal health authority before arranging movement. Wisconsin’s 2016 special-order announcement.

For suspected brucellosis, CDC tells veterinary teams to warn the receiving laboratory. Its recommended PPE for high-risk work includes gloves, a disposable gown, an N95 respirator and face or eye protection. Relevant activities include birth or abortion care, specimen collection, surgery and contaminated-environment cleaning. The clinic should plan those protections; owners should discuss how to avoid exposure rather than collect specimens themselves. CDC laboratory and staff precautions.

For infected dogs, CDC advises gloves when handling waste, thorough handwashing, limiting exposure to other people and animals, and ongoing testing. Ask the team to translate those measures into a household plan, including cleaning arrangements and a contact for questions about human exposure.

The South Carolina case shows how laboratory follow-up and exposure assessment can proceed together. A dog received a preliminary IFA diagnosis after an abortion; culture and PCR of vaginal secretions confirmed infection. Investigators identified 17 people and five animals exposed. Three people with high-risk exposure received clinician-directed prophylaxis and monitoring. The two household dogs initially tested negative, and their owners declined recommended 8-week follow-up. No secondary cases were identified. CDC MMWR, June 2024.

That report describes one investigation, not a treatment plan for another household. Tell a human healthcare professional or public health team about relevant contact with reproductive material and the dog’s test status. Decisions about human assessment, monitoring and medication belong with those professionals; a dog’s antibody result cannot diagnose a person.

If infection is supported, plan beyond the next result

CDC considers B. canis infection in dogs non-curable and warns that treated pets may continue shedding bacteria. Cornell likewise describes relapse and ongoing monitoring, and notes that sterilization reduces shedding without curing infection. A dog appearing well or completing treatment does not, by itself, settle the long-term management question. CDC ongoing-shedding warning; Cornell treatment limitations.

The human-health evidence also needs proportionate framing. An AVMA letter dated March 28, 2025 reported that fewer than 1% of human brucellosis cases were associated with B. canis, while acknowledging likely underreporting and the lack of a validated human serologic test. That percentage describes the share of reported human brucellosis cases, not the risk to an exposed owner. AVMA’s March 2025 status letter.

The same letter reported that CDC had initiated canine-brucellosis guideline development. It is a historical status report, not evidence that a national protocol was completed or remained in development throughout 2026. For current case decisions, the veterinary team should use the applicable laboratory and public health instructions.

Before ending the follow-up conversation, get a clear next action: the test being completed or ordered, the expected reporting date, whether another sample is needed, the reason and date for any retest, and the person responsible for calling. Keep the laboratory interpretation and any official restrictions together with that plan. This makes a non-negative screen a traceable follow-up process while the people responsible for diagnosis and public health resolve its meaning.

Sources

• Changes to Brucella canis Serology Testing - Cornell AHDC

• Brucella Multiplex Testing for Dogs - Cornell AHDC

• Canine brucellosis - Cornell Riney Canine Health Center

• Performance characteristics of three Brucella canis serological assays in the United States - Frontiers in Veterinary Science

• Update: Diagnostic Options for Canine Brucellosis - Kansas State Veterinary Diagnostic Laboratory

• VDL Brucella Testing - Iowa State University Veterinary Diagnostic Laboratory

• Brucella canis (Reportable Animal Diseases) - Montana Department of Livestock

• Veterinary Guidance for Brucellosis - CDC

• Notes from the Field: Multidisciplinary Approach to Investigating Brucella canis Exposures - South Carolina, September 2023 - CDC MMWR

• AVMA Response to USAHA Resolutions 22 and 23 on Canine Brucellosis - AVMA / USAHA

• Brucellosis in Dogs - Merck Veterinary Manual

• Wisconsin State Veterinarian Issues Special Order to Control Canine Brucellosis - Wisconsin DATCP