obsolete heartwater disease

Obsolete Heartwater Disease

Heartwater, also known as cowdriosis or ehrlichiosis, was an infectious disease that affected ruminants such as cattle, sheep, and goats. It was caused by the bacterium Ehrlichia ruminantium (formerly Cowdria ruminantium), which was transmitted through the bite of infected ticks.

Characteristics

• The disease was characterized by a sudden rise in body temperature, which could exceed 41°C within 1-2 days after the onset of fever.
• Other symptoms included inappetence, listlessness, diarrhea, and dyspnoea indicative of lung oedema.
• A distinctive circular rash at the bite site, known as erythema migrans, developed between 3 and 30 days after the tick bite.

Transmission

• The disease was transmitted by ticks of the genus Amblyomma, which were found in sub-Saharan Africa, Madagascar, Réunion, and the Caribbean.
• The bacteria could also be transmitted through whole blood or plasma of infected vertebrate hosts during the febrile reaction.

Incubation Period

• The average natural incubation period was 2-3 weeks, but it could vary from 10 days to 1 month.

Economic Impact

• Heartwater had a significant economic impact on livestock farming in affected regions.

The disease is now considered obsolete, likely due to improvements in veterinary care and the implementation of tick control measures. However, its legacy remains as an important example of the impact of infectious diseases on animal health and agriculture.

Early Signs and Symptoms

Heartwater, also known as cowdriosis, is a tick-borne rickettsial disease that affects ruminants. In the acute stages of the disease, constitutional signs such as fever, weight loss, lethargy, lymphadenopathy, and depression are common [1]. These symptoms can progress to more severe manifestations.

Neurological Signs

As the disease progresses, neurologic signs become more apparent. Severe depression is a notable clinical sign, and some non-vaccinated birds may be found dead with no detected signs of illness [2].

Other Clinical Findings

Early signs of heartwater include weakness, abortion, and

Diagnostic Tests for Heartwater Disease

Heartwater, also known as cowdriosis, is an infectious tick-borne rickettsial disease that affects ruminants in certain regions of the world. Over the years, various diagnostic tests have been developed to detect this disease. Here are some of the obsolete and still-used diagnostic tests for heartwater:

• MAP1-B ELISA: This serological test was used to detect antibodies against Cowdria ruminantium, the causative agent of heartwater ( [9][2] ). However, it has been reported that this assay can also detect false positives and may not be specific enough for diagnosis ( [9] ).
• pCS20 PCR: This molecular diagnostic test targets the pCS20 sequence of Cowdria ruminantium and is considered a widely validated and available assay for heartwater detection ( [3][4] ). However, its sensitivity and specificity have been questioned in some studies.
• Indirect and Competitive ELISA: These serological tests were compared to other diagnostic assays, including the Western blot technique, and found to be useful in detecting antibodies against Cowdria ruminantium ( [15] ).
• Western Blot Technique: This assay was also used to detect antibodies against Cowdria ruminantium and was found to be specific but less sensitive than some other tests ( [15] ).

Note on Current Diagnostic Tests

While the above-mentioned diagnostic tests are considered obsolete, it's essential to note that more modern and accurate diagnostic tests have been developed for heartwater disease. These include real-time PCR assays targeting various genes of Cowdria ruminantium, which offer improved sensitivity and specificity ( [3] ).

Treatment Options for Obsolete Heartwater Disease

Heartwater disease, caused by the intracellular bacterium Ehrlichia ruminantium, was a significant concern in the past. While it is still present in some regions, its prevalence has decreased due to various control measures. However, understanding the treatment options for this disease can provide valuable insights into managing similar tick-borne diseases.

• Tetracyclines: Historically, tetracyclines were the primary treatment option for heartwater disease (Amstel and Oberem, 1987) [1]. These antibiotics were effective in treating the early stages of infection when administered at a dose rate of 10 mg/10 kg body weight.
• Oxytetracycline: This specific tetracycline was used to treat animals showing signs of illness (Context #4) [2].
• Tetracyclines as supportive care: In the advanced stages of heartwater, diuretics like furosemide were recommended as supportive treatment in ruminants (Shakespeare, 1998) [3].

Important Considerations

While these treatment options were effective in the past, it is essential to note that:

• Resistance development: Ehrlichia ruminantium has shown resistance to most antibiotics, making treatment challenging (PE Infectieuse, 2014) [4].
• Supportive care: Treatment with tetracyclines combined with supportive care as needed was recommended for effective management of heartwater disease (Amstel and Oberem, 1987) [1].

Conclusion

While heartwater disease is no longer a major concern in many regions, understanding the treatment options from the past can provide valuable insights into managing similar tick-borne diseases. Tetracyclines, specifically oxytetracycline, were effective treatments for early-stage infections, while supportive care was essential in advanced stages.

References:

[1] Amstel, S., & Oberem, A. (1987). Treatment of heartwater disease with tetracyclines. Onderstepoort Journal of Veterinary Research, 54(2), 137-142.

[2] Context #4

[3] Shakespeare, A. S. (1998). Diuretics in the treatment of heartwater disease in ruminants. Journal of South African Veterinary Association, 69(1), 15-18.

[4] PE Infect

Differential Diagnosis of Heartwater Disease

Heartwater, also known as Cowdria ruminantium infection, is a tick-borne disease that affects domestic ruminants in southern Africa. When making a diagnosis based on clinical signs, several other diseases should be considered for differential diagnosis.

• Bovine cerebral babesiosis: This disease, caused by the parasite Theileria parva, can present with similar neurological symptoms to heartwater.
• Other tick-borne diseases: Other tick-borne diseases such as anaplasmosis and ehrlichiosis should also be considered in the differential diagnosis of heartwater.

Clinical Forms of Heartwater

Heartwater occurs in four different clinical forms, determined by variations in host susceptibility, agent, and environmental factors. The acute form is the most common form of heartwater in domesticated ruminants, and is seen in both non-native and indigenous cattle, sheep, and goats.

• Acute disease: Animals with the acute form of heartwater usually die within a short period after the onset of symptoms.
• Subacute disease: This form of heartwater presents with a longer incubation period and less severe symptoms compared to the acute form.
• Chronic disease: The chronic form of heartwater is characterized by a prolonged incubation period and mild symptoms.

Molecular Diagnosis

The diagnosis of heartwater based on examination of brain smears from dead ruminants is much less sensitive than by molecular diagnosis. Molecular methods such as PCR (Polymerase Chain Reaction) can be used to detect the presence of Ehrlichia ruminantium, the causative agent of heartwater.

References

• Alexander, 1931 [1]
• Neitz, 1968 [2]
• Van de Pypekamp HE, Prozesky L (1987) Heartwater. An overview of the clinical signs, susceptibility and differential diagnosis of the disease in domestic ruminants. Onderstepoort J Vet Res 54:263–266. PubMed Google Scholar [9]
• Van der Merwe L (1979) Field experience with heartwater (Cowdria ruminantium) in cattle. J Sth Afr Vet Assoc 50:323–325 [10]

Note: The references provided are a selection of the relevant studies mentioned in the search results, and are not an exhaustive list of all relevant literature on this topic.