Diagnostic Strategies for Crimean–Congo Hemorrhagic Fever (CCHF) in Humans, Animals, and Ticks with Emphasis on Biosafety and Sampling Risks

 

 

Dr. Majed Hamed Al Saegh / poultry pathologist / Australia

Introduction

Crimean–Congo hemorrhagic fever (CCHF) is one of the most lethal and widespread viral hemorrhagic fevers in rural and peri-urban areas of Asia, Africa, the Middle East, and parts of Europe. Caused by the CCHFV virus from the Nairoviridae family, it is classified as a Biosafety Level 4 (BSL-4) pathogen. Transmission occurs through tick bites—particularly from Hyalomma species—or through contact with infected blood or bodily fluids, whether human or animal. The global absence of an effective vaccine or specific antiviral treatment makes early diagnosis and surveillance a critical public health priority.

 

Due to its zoonotic nature, effective diagnosis of CCHF requires a One Health approach that integrates human, veterinary, and environmental health sectors. This report reviews diagnostic strategies in humans, animals, and ticks, while also discussing biosafety challenges in sample collection and offering practical proposals for strengthening field diagnostics and response systems.

 

1. Diagnosis of CCHF in Humans
2. Clinical and Laboratory Features

Initial clinical signs are nonspecific and flu-like, including fever, headache, muscle pain, nausea, and fatigue. Within a few days, the condition may progress to a hemorrhagic rash, oral and nasal bleeding, internal bleeding, and organ failure. Laboratory findings include thrombocytopenia, elevated liver enzymes, and leukopenia. Identifying these markers is crucial for early suspicion of CCHF.

 

2. Molecular Diagnosis

RT-PCR is the gold standard for early detection, performed on whole blood, plasma, or other bodily fluids. It has high sensitivity during the acute phase (first 5 days) and typically targets conserved regions of the viral genome, such as the S gene. Techniques like LAMP and RPA are being evaluated for use in low-resource settings due to their simplicity and rapid results, though they still require broader field validation.

 

3. Serological Testing

ELISA is used to detect IgM and IgG antibodies during the later stages (post day 5). In severe cases, immune responses may be delayed or weak. It is therefore recommended to combine molecular and serological testing. Recombinant nucleoproteins are employed to enhance ELISA accuracy.

 

4. Emerging Technologies

Promising new tools include lateral flow assays (LFA) and portable point-of-care devices. These are under evaluation and not yet widely implemented. Additionally, efforts to integrate CRISPR-based detection systems for viral RNA are underway, showing potential for sensitive and rapid field diagnostics.

 

1. Diagnosis of CCHF in Animals
2. Role in the Transmission Cycle

Animals are asymptomatic but develop short-term viremia (3–7 days), playing a critical role in maintaining the virus cycle between ticks and humans. Commonly affected species include cattle, sheep, goats, camels, and horses.

 

2. Serological Testing

IgG antibodies can be detected via ELISA, indicating prior exposure. These results are vital for epidemiological surveillance. However, a major limitation is the lack of standardized, commercially approved test kits for all livestock species, complicating regional comparisons.

 

3. Molecular Diagnosis

RT-PCR is applicable during the viremia phase, but the brief window requires precise timing for sampling. Blood samples or post-mortem tissues such as spleen and lymph nodes are typically used. Currently, no universally standardised protocols exist for animal sample collection.

 

III. Diagnosis of CCHF in Ticks

1. Epidemiological Significance

Hyalomma ticks serve as both vector and natural reservoir. The virus can be transmitted vertically (transovarial) or horizontally (through feeding on infected hosts).

 

2. Diagnostic Methods

Ticks are collected from animals or the environment and processed for laboratory analysis. RT-PCR targets viral genome regions, especially the S gene. Advanced sequencing methods like next-generation sequencing (NGS) help track viral evolution and genotype distribution.

 

3. Collection and Processing Challenges

Tick collection requires special training and is one of the riskiest surveillance activities due to infection risks. Live tick transport and storage demand strict biosafety protocols.

 

1. Biosafety and Sampling Risks
2. Biological Classification and Hazards

CCHFV is classified as BSL-4 due to its high lethality and human-to-human transmissibility. Sample collection and processing present significant biosafety challenges, with reported lab-acquired infections and fatalities linked to insufficient precautions.

 

2. Personal Protective Equipment (PPE)

Protective equipment must include impermeable suits, double gloves, safety goggles, powered air-purifying respirators (PAPRs), and protective boots. Samples should only be processed in BSL-3 or BSL-4 biosafety cabinets.

 

3. Sample Inactivation

Inactivating the virus before transport is essential. Standard methods include heating at 56°C for 30 minutes or using chemical disinfectants like sodium hypochlorite. Some inactivation agents may compromise downstream molecular assays, so careful reagent selection is required.

 

4. Transport and Disposal

Samples must be shipped under UN2814 or UN3373 guidelines. Waste disposal should be via high-temperature incineration or certified autoclaving. Personnel must be routinely trained in these protocols.

 

1. Challenges and Future Directions
2. Genetic Mutations and Diagnostic Efficacy

Rapid viral mutation reduces RT-PCR reliability. Broad-spectrum primers and NGS-based surveillance are essential to track viral genetic diversity.

 

2. Lack of Rapid Field Diagnostics

The absence of fast, portable diagnostic tools hinders timely responses in remote settings. Tools must be affordable, user-friendly, and not electricity-dependent.

 

3. Gaps in Animal Diagnostics

There is an urgent need for standardized, validated diagnostic kits for all livestock. The current lack of tools delays early detection and weakens early warning systems.

 

4. Integration of AI and Big Data

Artificial intelligence can analyse surveillance data to predict hotspots and enhance response coordination. This requires harmonised data-sharing across human, veterinary, and environmental health sectors.

 

Conclusion

Diagnosing CCHF requires an integrated, multi-sectoral strategy that combines molecular and serological diagnostics while upholding biosafety standards. Key obstacles include infrastructure gaps, limited field diagnostics, and the lack of unified protocols. Investment in capacity building, rapid and safe diagnostic tools, and adoption of the One Health approach are fundamental to reducing virus spread, particularly in endemic countries like Iraq, Afghanistan, Turkey, and Iran. Regional cooperation and data exchange are critical to strengthening our collective response to this persistent health threat.